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PubMed1989

Role of glutamine aminotransferase in glutamine catabolism by Saccharomyces cerevisiae under microaerophilic conditions.

The involvement of glutamine aminotransferase activity in glutamine catabolism by Saccharomyces cerevisiae under microaerophilic conditions was studied. We were able to show that there are at least two different glutamine aminotransferase activities that are differentiated genetically, by their substrate specificity (pyruvate and glyoxylate dependence), and their different modes of regulation. The pyruvate-dependent glutamine aminotransferase activity plays a major role in glutamine catabolism under microaerophilic conditions since the wild-type strain S288C showed a 10-fold higher activity in static cultures than in agitated ones. The same strain also had 3-fold higher glutaminase B activity in agitated cultures than in static ones. Pyruvate-dependent glutamine aminotransferase activity is not regulated directly by O2 itself since a rho- strain showed a high activity regardless of the extent of aeration of cultures. Finally, we were able to isolate a mutant, strain CN20, derived from the rho- strain and unable to utilize glutamine as the sole nitrogen source, which was severely affected in pyruvate-dependent but not in glyoxylate-dependent aminotransferase activity.

Aerobiosis↗

PubMed1989

Biosynthesis of Tetrapyrrole Pigment Precursors : Pyridoxal Requirement of the Aminotransferase Step in the Formation of delta-Aminolevulinate from Glutamate in Extracts of Chlorella vulgaris.

The aminotransferase that catalyzes the formation of delta-aminolevulinic acid from glutamate-1-semialdehyde or from glutamate in a reconstituted enzyme system was isolated and partially purified from Chlorella vulgaris. The apparent molecular weight of the aminotransferase was determined by Sephadex G-100 and Ultrogel AcA 54 gel filtration to be 60,000 +/- 5,000. Catalytic activity of the aminotransferase required pyrixodal phosphate (PALP). The cofactor could not be removed by gel filtration after exposure of the enzyme to PALP. Aminotransferase was inhibited by gabaculine (3-amino-2,3-dihydrobenzoic acid). The concentration of gabaculine required for half maximal inhibition was about 0.05 micromolar. Aminotransferase activity could be regained upon the removal of gabaculine by gel filtration and supplementing the assay medium with PALP. Neither the inhibitory action of gabaculine nor its reversibility was affected by preincubation of the enzyme with the keto acids levulinate and delta-aminolevulinic acid.

Journal Article↗

PubMed1989

Specificity of aspartate aminotransferases from leguminous plants for 4-substituted glutamic acids.

Aspartate aminotransferase (glutamate-oxalacetate transaminase) was partially purified from extracts of germinating seeds of peanut (Arachis hypogaea), honey locust (Gleditsia triacanthos), soybean (Glycine max), and Sophora japonica. The ability of these enzyme preparations, as well as aspartate aminotransferase purified from pig heart cytosol, to use 4-substituted glutamic acids as amino group donors and their corresponding 2-oxo acids as amino group acceptors in the aminotransferase reaction was measured. All 4-substituted glutamic acid analogs tested were poorer substrates than was glutamate or 2-oxoglutarate. 2-Oxo-4-methyleneglutarate was least effective (lowest relative V(m)/K(m)) as a substrate for the enzyme from peanuts and honey locust, which are the two species studied that accumulate 4-methyleneglutamic acid and 4-methyleneglutamine. Of the different aminotransferases tested, the enzyme from honey locust was the least active with 2-oxo-4-hydroxy-4-methylglutarate, the corresponding amino acid of which also accumulates in that species. These results suggest that transamination of 2-oxo-4-substituted glutaric acids is not involved in the biosynthesis of the corresponding 4-substituted glutamic acids in these species. Rather, accumulation of certain 4-substituted glutamic acids in these instances may be, in part, the result of the inefficacy of their transamination by aspartate aminotransferase.

Journal Article↗

PubMed2005

Enzyme adaptation to alkaline pH: atomic resolution (1.08 A) structure of phosphoserine aminotransferase from Bacillus alcalophilus.

The crystal structure of the vitamin B(6)-dependent enzyme phosphoserine aminotransferase from the obligatory alkaliphile Bacillus alcalophilus has been determined at 1.08 A resolution. The model was refined to an R-factor of 11.7% (R(free) = 13.9%). The enzyme displays a narrow pH optimum of enzymatic activity at pH 9.0. The final structure was compared to the previously reported structure of the mesophilic phosphoserine aminotransferase from Escherichia coli and to that of phosphoserine aminotransferase from a facultative alkaliphile, Bacillus circulans subsp. alkalophilus. All three enzymes are homodimers with each monomer comprising a two-domain architecture. Despite the high structural similarity, the alkaliphilic representatives possess a set of distinctive structural features. Two residues directly interacting with pyridoxal-5'-phosphate are replaced, and an additional hydrogen bond to the O3' atom of the cofactor is present in alkaliphilic phosphoserine aminotransferases. The number of hydrogen bonds and hydrophobic interactions at the dimer interface is increased. Hydrophobic interactions between the two domains in the monomers are enhanced. Moreover, the number of negatively charged amino acid residues increases on the solvent-accessible molecular surface and fewer hydrophobic residues are exposed to the solvent. Further, the total amount of ion pairs and ion networks is significantly reduced in the Bacillus enzymes, while the total number of hydrogen bonds is increased. The mesophilic enzyme from Escherichia coli contains two additional beta-strands in a surface loop with a third beta-strand being shorter in the structure. The identified structural features are proposed to be possible factors implicated in the alkaline adaptation of phosphoserine aminotransferase.

Adaptation, Physiological↗

PubMed1999

Crystal structure of Trypanosoma cruzi tyrosine aminotransferase: substrate specificity is influenced by cofactor binding mode.

The crystal structure of tyrosine aminotransferase (TAT) from the parasitic protozoan Trypanosoma cruzi, which belongs to the aminotransferase subfamily Igamma, has been determined at 2.5 A resolution with the R-value R = 15.1%. T. cruzi TAT shares less than 15% sequence identity with aminotransferases of subfamily Ialpha but shows only two larger topological differences to the aspartate aminotransferases (AspATs). First, TAT contains a loop protruding from the enzyme surface in the larger cofactor-binding domain, where the AspATs have a kinked alpha-helix. Second, in the smaller substrate-binding domain, TAT has a four-stranded antiparallel beta-sheet instead of the two-stranded beta-sheet in the AspATs. The position of the aromatic ring of the pyridoxal-5'-phosphate cofactor is very similar to the AspATs but the phosphate group, in contrast, is closer to the substrate-binding site with one of its oxygen atoms pointing toward the substrate. Differences in substrate specificities of T. cruzi TAT and subfamily Ialpha aminotransferases can be attributed by modeling of substrate complexes mainly to this different position of the cofactor-phosphate group. Absence of the arginine, which in the AspATs fixes the substrate side-chain carboxylate group by a salt bridge, contributes to the inability of T. cruzi TAT to transaminate acidic amino acids. The preference of TAT for tyrosine is probably related to the ability of Asn17 in TAT to form a hydrogen bond to the tyrosine side-chain hydroxyl group.

Amino Acid Sequence↗

PubMed1978

Tyrosine aminotransferase in AKR/J albino and C57BL/6J black mouse skin.

L-Tyrosine aminotransferase is present in a high speed supernatant fraction of skin homogenate of AKR/J albino and C57BL/6J black mice. The conversion of tyrosine to p-hydroxyphenylpyruvate was shown to be catalyzed by an aminotransferase by the following observations: the reaction was partially dependent on the presence of low concentrations of alpha-ketoglutarate; catalase was ineffective in increasing the yield of p-hydroxyphenylpyruvate; there was potent inhibition by typical inhibitors of pyridoxal phosphate enzymes and of rat liver tyrosine aminotransferase; there was no inhibition by inhibitors of L-amino acid oxidase; and there was no oxidation of L-leucine, the best substrate for rat kidney L-amino acid oxidase. The aminotransferase was stimulated by mercaptoethanol and was inhibited by high concentrations of alpha-ketoglutarate. The apparent Km for tyrosine was 5 X 10(-3) M and the molecular weight, determined by sucrose density gradient centrifugation, was 150-200,000. Dopa was also transaminated by the crude enzyme. No tyrosine aminotransferase could be detected in extracts of hamster melanoma.

Amino Acid Oxidoreductases↗

PubMed1978

Cycloheximide causes increased accumulation of translatable mRNA for tyrosine aminotransferase and tryptophan oxygenase in livers of cortisol-treated rats.

Messenger RNA activities for two cortisol-inducible enzymes, tyrosine aminotransferase and tryptophan oxygenase, have been determined by translation in a wheat germ system. The effects of cycloheximide on the two mRNA activities have been evaluated. Cortisol leads to an increase of the translatable mRNAs for tyrosine aminotransferase and tryptophan oxygenase with a maximum at approximately 6 h. Cycloheximide was administered 4 h after treatment with cortisol; 2 h later, the activities of tyrosine aminotransferase and tryptophan oxygenase mRNA had increased five-fold and two-fold, respectively, compared to the activities reached with cortisol alone. Thereafter the amount of the two translatable mRNAs declined, though 14 h after cortisol administration the mRNA activities were still several fold higher than in control animals. Application of alpha-amanitin together with cycloheximide did not prevent an increased accumulation of specific translatable mRNAs. The increase in tyrosine aminotransferase and tryptophan oxygenase activity by cortisol was immediately blocked by cycloheximide. Whereas tryptophan oxygenase activity rapidly declined after cycloheximide application, tyrosine aminotransferase activity remained at the same level. Approximately 4 h thereafter, both enzyme activities increased again.

Amanitins↗

PubMed1982

Positive and negative cAMP-mediated control of tyrosine aminotransferase synthesis in Reuber H35 hepatoma cells.

Induction of L-tyrosine:2-oxoglutarate aminotransferase (EC 2.6.1.5) by N6,O2'-dibutyryl-adenosine 3',5'-monophosphate (Bt2cAMP) in Reuber H35 hepatoma cells reaches a maximum value between 3-5 h after addition of Bt2cAMP and subsequently decreases in the continuous presence of Bt2cAMP. We have investigated the kinetics of the increase, i.e. induction, and the decrease, i.e. the repressed state, of the tyrosine-aminotransferase-synthesizing system under these conditions. Our experimental results are as follows. 1. The repressed state of the tyrosine-aminotransferase-synthesizing system is not caused by a decrease in the intracellular cAMP concentration. 2. The repressed state is inhibited by actinomycin D (while induction is not inhibited). 3. During the repressed state no effect of dexamethasone on tyrosine aminotransferase synthesis is found, while during induction Bt2cAMP and dexamethasone act synergistically. 4. Longer starvation of the cells in serum-free medium has no influence on the kinetics of the induction/repressed state curve. From these results we have concluded that the mechanism of the transition to the repressed state of the tyrosine-aminotransferase-synthesizing system is essentially different from the mechanism of deinduction which occurs after removal of the inducer. Moreover, the repressed state of the system is a phenomenon which is induced by Bt2cAMP separately from induction at a different level of protein synthesis.

Animals↗

PubMed1991

Characterization of glutamate-1-semialdehyde aminotransferase of Synechococcus. Steady-state kinetic analysis.

Synechococcus glutamate-1-semialdehyde aminotransferase was expressed in large amounts in transformed cells of Escherichia coli. The resulting purified enzyme has an absorption spectrum characteristic of B6-containing enzymes and could be converted to the pyridoxal-phosphate form with excess dioxovalerate (O2Val), and back to the pyridoxamine-phosphate form with diaminovalerate (A2Val). Both enzyme forms are similarly active in the conversion of glutamate 1-semialdehyde (GSA) to 5-aminolevulinate (ALev), suggesting that A2Val and O2Val are intermediates. Initial rates of ALev synthesis at various fixed concentrations of GSA followed typical Michaelis-Menten kinetics (Km of GSA for the pyridoxamine-phosphate form of GSA aminotransferase = 12 microM, kcat = 0.23 s-1). In submicromolar amounts A2Val stimulates ALev synthesis, and in a series of concentrations with various fixed concentrations of GSA, gives a family of parallel lines in Lineweaver-Burk plots (Km for A2Val = 1.0 microM). On the other hand, O2Val gives competitive inhibition of the pyridoxamine-phosphate form of GSA-aminotransferase and mixed-type inhibition of the pyridoxal-phosphate form (Ki for O2Val = 1.4 mM). In general the kinetics were typical of ping-pong bi-bi mechanisms in which A2Val is the second substrate (intermediate) and O2Val is an alternative first substrate. There is no compelling evidence that O2Val accepts an amino group at its C5 position resulting in the direct formation of ALev, or the reverse involving the apparent formation of O2Val from ALev. These results are consistent with the hypothesis that the mechanism of GSA aminotransferase mimics that of other aminotransferases and that A2Val is the intermediate.

Chromatography, Ion Exchange↗

PubMed1993

Homology of pyridoxal-5'-phosphate-dependent aminotransferases with the cobC (cobalamin synthesis), nifS (nitrogen fixation), pabC (p-aminobenzoate synthesis) and malY (abolishing endogenous induction of the maltose system) gene products.

Bacterial deletion mutants have indicated that the gene products of cobC, nifS, pabC and malY participate in important metabolic pathways, i.e. cobalamin synthesis, nitrogen fixation, synthesis of p-aminobenzoate and the regulation of the maltose system, respectively. However, the proteins themselves and their specific functions have not yet been identified. In the course of our studies on the evolutionary relationships among aminotransferases, we have found that the above gene products are homologous to aminotransferases. Profile analysis [Gribskov, M., Lüthy, R. & Eisenberg, D. (1990) Methods Enzymol. 183, 146-159] based on the amino acid sequences of certain subgroups of aminotransferases as probes attributed significant Z scores in the range 5-20 SD to the deduced amino acid sequences of the above gene products as included in the protein data base. Reciprocal profile analyses confirmed the homologies. All known aminotransferases are pyridoxal-5'-phosphate-dependent enzymes and catalyze the reversible transfer of amino groups from amino acids to oxo acids. The sequence homologies suggest that the above gene products are aminotransferases or other closely related pyridoxal-5'-phosphate-dependent enzymes probably catalyzing transformations of amino acids involving cleavage of a bond at C alpha.

4-Aminobenzoic Acid↗

PubMed2006

The narrow substrate specificity of human tyrosine aminotransferase--the enzyme deficient in tyrosinemia type II.

Human tyrosine aminotransferase (hTATase) is the pyridoxal phosphate-dependent enzyme that catalyzes the reversible transamination of tyrosine to p-hydrophenylpyruvate, an important step in tyrosine metabolism. hTATase deficiency is implicated in the rare metabolic disorder, tyrosinemia type II. This enzyme is a member of the poorly characterized Igamma subfamily of the family I aminotransferases. The full length and truncated forms of recombinant hTATase were expressed in Escherichia coli, and purified to homogeneity. The pH-dependent titration of wild-type reveals a spectrum characteristic of family I aminotransferases with an aldimine pK(a) of 7.22. I249A mutant hTATase exhibits an unusual spectrum with a similar aldimine pK(a) (6.85). hTATase has very narrow substrate specificity with the highest enzymatic activity for the Tyr/alpha-ketoglutarate substrate pair, which gives a steady state k(cat) value of 83 s(-1). In contrast there is no detectable transamination of aspartate or other cosubstrates. The present findings show that hTATase is the only known aminotransferase that discriminates significantly between Tyr and Phe: the k(cat)/K(m) value for Tyr is about four orders of magnitude greater than that for Phe. A comparison of substrate specificities of representative Ialpha and Igamma aminotransferases is described along with the physiological significance of the discrimination between Tyr and Phe by hTATase as applied to the understanding of the molecular basis of phenylketonuria.

Amino Acid Substitution↗

PubMed2000

Characterization and role of the branched-chain aminotransferase (BcaT) isolated from Lactococcus lactis subsp. cremoris NCDO 763.

In Lactococcus lactis, which is widely used as a starter in the cheese industry, the first step of aromatic and branched-chain amino acid degradation is a transamination which is catalyzed by two major aminotransferases. We have previously purified and characterized biochemically and genetically the aromatic aminotransferase, AraT. In the present study, we purified and studied the second enzyme, the branched-chain aminotransferase, BcaT. We cloned and sequenced the corresponding gene and used a mutant, along with the luciferase gene as the reporter, to study the role of the enzyme in amino acid metabolism and to reveal the regulation of gene transcription. BcaT catalyzes transamination of the three branched-chain amino acids and methionine and belongs to class IV of the pyridoxal 5'-phosphate-dependent aminotransferases. In contrast to most of the previously described bacterial BcaTs, which are hexameric, this enzyme is homodimeric. It is responsible for 90% of the total isoleucine and valine aminotransferase activity of the cell and for 50 and 40% of the activity towards leucine and methionine, respectively. The original role of BcaT was probably biosynthetic since expression of its gene was repressed by free amino acids and especially by isoleucine. However, in dairy strains, which are auxotrophic for branched-chain amino acids, BcaT functions only as a catabolic enzyme that initiates the conversion of major aroma precursors. Since this enzyme is still active under cheese-ripening conditions, it certainly plays a major role in cheese flavor development.

Amino Acids, Branched-Chain↗

PubMed1976

Regulation of histidinol phosphate aminotransferase synthesis by tryptophan in Bacillus subtilis.

The effect of tryptophan on the synthesis of histidinol phosphate aminotransferase and prephenate dehydrogenase has been examined. The genes specifying two enzymes for tryptophan biosynthesis (anthranilate synthase and tryptophan synthase-B) were found to be derepressed in a temporal sequence according to their chromosomal location. The genes for histidinol phosphate aminotransferase and prephenate dehydrogenase were derepressed simultaneously approximately 8 min after tryptophan synthase-B. When excess tryptophan was added to a derepressed culture, the pattern of repression of trpE (anthranilate synthase), trpB (tryptophan synthase-B), hisH (histidinol phosphate aminotransferase), and tyrA (prephenate dehydrogenase) was found to be simultaneous. Methyl tryptophan-resistant mutants, which synthesize elevated levels of the tryptophan enzymes, also synthesized elevated levels of histidinol phosphate aminotransferase. Qualitatively similar data were obtained in a temperature-sensitive tryptophanyl-transferase ribonucleic acid synthetase mutant grown at elevated temperatures. The time at which messenger ribonucleic acid was synthesized for anthranilate synthase, tryptophan synthase-B, histidinol phosphate aminotransferase, and prephenate dehydrogenase in the presence of actinomycin D indicated that ordered enzyme synthesis was a result of ordered transcription of the corresponding portion of the genome. The effect of the drug rifampin on enzyme synthesis was also examined. The addition of this drug halted the transcription of anthranilate synthase very rapidly, but later regions of the tryptophan region continued to be transcribed. The transcription of the hisH and tyrA genes was also shut off rapidly after rifampin was added. The significance of these observations to the control of transcription of the hisH gene by tryptophan is discussed.

Anthranilate Synthase↗

PubMed2003

Influence of hepatitis B virus virema upon serum aminotransferase activity in dialysis population.

BACKGROUND: The control of the spread of hepatitis B virus (HBV) infection within dialysis units has been one of the major advances in the management of patients with end-stage renal disease (ESRD). However, clinical and biochemical expression of HBV in dialysis patients have not been adequately addressed. Elevated values of serum aminotransferase activity are a sensitive measure of hepatocellular injury, but the role of HBV infection in the development of liver disease among dialysis patients has not been adequately analysed. Also, the clinical impact related to the virological characteristics of HBV in dialysis has not been evaluated. METHODS: Demographic, biochemical and virological data from 727 patients undergoing chronic dialysis in seven dialysis units in northern Italy were collected in order to assess the biochemical consequences related to the presence of HBV infection in this population. We have measured by RT-PCR technology the titers of HBV viremia in HBsAg positive patients receiving dialysis. RESULTS: Univariate analysis showed that AST and ALT values were significantly higher in HBsAg positive/HBV DNA positive than HBsAg negative patients on dialysis; AST, 22.86+/-31.34 vs. 14.19+/-9.7 IU/L (P=0.00001); and ALT, 25.07+/-41.59 vs. 13.9+/-41.59 IU/L (P=0.00001). In the subgroup of HBsAg positive patients, the frequency of detectable HBeAg in serum was 14.9% (7/47). The median value of HBV DNA in patients with detectable HBV DNA in serum was 2.160 x 10(3) copies/mL (range, 2.5 x 10(2)-4 x 10(6) copies/mL). HBsAg positive/HCV positive patients had higher aminotransferase activity than other subgroups (P=0.0001). Multivariate analysis showed a significant and independent association between detectable HBsAg/HBV DNA in serum and AST (P=0.00001) and ALT (P=0.0001) activity AST and ALT levels were lower in dialysis than healthy individuals--this finding persisted in age- and gender-matched comparisons. CONCLUSIONS: The HBV viral load in HBsAg positive patients receiving maintenance dialysis is not high. HBsAg positivity with detectable HBV DNA in serum is a strong and independent predictor of raised aminotransferase activity among dialysis patients. HBsAg positive patients had greater aminotransferase activity than HBsAg negative individuals even if both the groups had mean aminotransferase levels within the normal range considered for healthy population. Clinical trials aimed at identifying the best cut-off value to enhance the diagnostic yield of AST/ALT for detecting HBV in dialysis population are under way.

Adult↗

PubMed1986

Immunohistochemical localization of ornithine aminotransferase in normal rat tissues by Fab'-horseradish peroxidase conjugates.

Immunohistochemical localization of ornithine aminotransferase (L-ornithine: 2-oxo-acid aminotransferase, EC 2.6.1.13), a mitochondrial enzyme whose hereditary absence induces gyrate atrophy of the choroid and retina, was elucidated by a direct immunoperoxidase method using Fab'-horseradish peroxidase conjugates. In immunodiffusion studies, the antibodies raised with the re-crystallized enzyme were highly specific to ornithine aminotransferase. To show localization of ornithine aminotransferase in normal rat tissues, clear immunohistochemical staining of this enzyme through the inner mitochondrial membrane in paraffin sections was achieved with Fab'-horseradish peroxidase conjugates. Strong immunoreactivity was present in cerebral neurons, hepatocytes, and epithelial cells of renal tubuli, gut mucous membranes, and ocular tissues. Specific distribution of ornithine aminotransferase was found in ependymal cell groups: namely, epithelial cells of the choroid plexus, pigmented and nonpigmented epithelial cells of the ciliary body. and Müller cells and pigment epithelium of the retina.

Animals↗

PubMed1992

Beta-lactams: a new class of conformationally-rigid inhibitors of gamma-aminobutyric acid aminotransferase.

A structural similarity of several monobactams (2-4), 3-aminonocardicinic acid (6), 6-aminopenicillanic acid (7), 7-aminocephalosporanic acid (8), and 7-aminodesacetoxycephalosporanic acids (9, 10) to gamma-aminobutyric acid (GABA) and to known inhibitors and substrates of GABA aminotransferase is described. Because of this, the above-mentioned compounds were tested as competitive inhibitors and as inactivators of pig brain GABA aminotransferase. All of the compounds were competitive inhibitors of GABA aminotransferase. On the basis of the inhibitory potency of these conformationally-rigid GABA analogues it is hypothesized that GABA is bound at the active site with its amino and carboxylate groups in a syn orientation. None of the compounds inactivates GABA aminotransferase. These beta-lactam analogues represent the first examples of a new class of inhibitors of GABA aminotransferase.

4-Aminobutyrate Transaminase↗

PubMedDate not supplied

Epidemiology of serum aminotransferase activities in the elderly.

BACKGROUND: Our study used data collected in Chung-Hsing Village in May 1998 to explore the distribution of serum aminotransferase activities and the relationship between aminotransferase and its related factors in the elderly. METHODS: All individuals aged 65 and over were recruited as study subjects. A total of 1093 persons, out of 1774 registered residents, were contacted by face-to-face interview. The response rate was 61.6 percent. However, only 586 subjects had blood tests and completed questionnaires. Analysis in this study was based on these 586 subjects. In order to study the significant related factors of abnormal aminotransferase activities, the t-test, ANOVA, chi-square analysis, and multivariate logistic regression were used. RESULTS: There were 66 percent men and 34 percent women. The mean age was 73.1 +/- 5.3 years. The mean values of aspartate aminotransferase (AST) were 29.3 +/- 14.5 u/l in men and 27.8 +/- 10.7 u/l in women (p > .05). The mean values of alanine aminotransferase (ALT) were 30.9 +/- 25.2 u/l in men and 26.3 +/- 12.6 u/l in women (p < .01). The abnormality rates of AST (> or = 40 u/l) were 10.5 percent in men and 12.2 percent in women (p > .05). The abnormality rates of ALT (> or = 40 u/l) were 16.7 percent in men and 12.6 percent in women (p > .05). After controlling for the other covariates, the multivariate logistic regression analysis showed that the significant related factor of abnormal AST was retirement status (odds ratio 4.4; 95 percent confidence interval = 1.5-13.3; p < .01). The significant related factors of abnormal ALT were obesity (odds ratio = 2.2; 95 percent confidence interval = 1.1-4.2; p < .05) and hypertriglyceridemia (odds ratio = 2.7; 95 percent confidence interval = 1.5-4.9; p < .01). CONCLUSIONS: We raise the hypothesis that evidence of liver disease with abnormal ALT may co-vary with other indicators of chronic diseases. A large-scale investigation will be suggested in the future to demonstrate the causal-effect issue between abnormal ALT and obesity or hypertriglyceridemia.

Aged↗

PubMed1977

Phenylalanine hydroxylase and tyrosine aminotransferase in human fetal and adult liver.

The mean value of phenylalanine hydroxylase activity in adult human liver was almost twice as high as that in the fetal ones; no consistent variations were seen with sex, fetal age (between the 11th and 22nd week of gestation), or with hours between delivery and death. The tyrosine aminotransferase levels did not correlate with sex, age, or method of abortion; however, they were 5 times higher in the two fetuses which survived for more than 1.5 hr after delivery. The mean concentration of tyrosine aminotransferase (excluding these two fetuses) was about 15 times lower than in the adult liver. Phenylalanine hydroxylase is known to appear in rat liver on the 20th to 21st day of gestation. Tyrosine aminotransferase, on the other hand, emerges on the first postnatal day and, as shown here, can be evoked by premature delivery. Thus, in man as in the rat, (1) phenylalanine hydroxylase approaches physiologically significant levels at an earlier development stage than does tyrosine aminotransferase and (2) extrauterinization stimulates the synthesis of tyrosine aminotransferase but not of phenylalanine hydroxylase. Speculation There is a greater analogy than is usually assumed between human and rat liver with respect to the time schedule of enzymic differentiation and the factors which regulate it.

Adult↗