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At least 829 records · Page 46Linked to original sources
PubMed1977

Asparagine transaminase from rat liver.

Asparagine transaminase has been purified about 200-fold from rat liver. The enzyme has a broad specificity toward both amino acids and alpha-keto acids. Thus, amino acids substituted in the beta position such as asparagine, S-methylcysteine, phenylalanine, cysteine, serine, and aspartate are substrates. The enzyme is also active with alanine, methionine, homoserine, alpha-aminobutyrate, glutamine, and leucine. The enzyme has a high affinity for glyoxylate but the affinity falls off markedly through the series glyoxylate, pyruvate, alpha-ketoburyrate, alpha-Keto acids substituted in the beta or gamma position, such as alpha-ketosuccinamate, phenylpyruvate, p-hydroxyphenylpyruvate, alpha-keto-gamma-methiolburyrate, and alpha-keto-gamma-hydroxybutyrate, are substrates for the enzyme. Amino acids or alpha-keto acids possessing a branch point at the beta carbon are inactive. Kinetic analysis of the asparagine glyoxylate transamination reaction is consistent with a ping-pong mechanism.

Amino Acids↗
PubMedDate not supplied

Prevalence of hepatitis B surface and e antigens, risk factors for viral acquisition and serum transaminase among blood donors in Ibadan, Nigeria.

The objective of this study was to determine the prevalence of hepatitis B e antigen (HBeAg) in blood donors with hepatitis B surface antigen (HBsAg), and alaninine transaminases (ALT) levels and possible risk factors for the transmission of hepatitis B virus (HBV). Over a 6-month period, consecutive blood donors were screened for HBsAg, HBeAg, ALT and risk factors for HBV transmission. One hundred seventy-five adults (158 males, 17 females) were screened. Thirty-seven (21.3%) were HBsAg positive, 4 (2.3%) were HBeAg Positive and 17 (9.7%) had a raised ALT level, which ranged between 42-126 IU/L. All the HBeAg-positive subjects had raised ALT levels. The main risk factors among others, were scarification and indiscriminate injections. Twenty of the 37 HBsAg-positive subjects (54%) had no identifiable risk factor. The present study revealed that, HBeAg positivity among HBsAg positive blood donors was infrequent and whenever present was associated with active liver disease indicated by raised ALT value.

Adolescent↗
PubMedDate not supplied

[The role of transaminases in realizing the protective effect of L-aspartate in hypoxia].

Activation of aspartate aminotransferase and alanine aminotransferase of mitochondria introduced to the incubation medium of pyridoxal-5'-phosphate (40 microM) is approximately 2 times higher than that of the corresponding cytoplasmic forms. At hypoxia aspartate aminotransferase activity in mitochondria and postmitochondrial supernatant tends to an increase while that of alanine aminotransferase decreases (above 2 times). The protection from hypoxic damage when using L-aspartate (100 mg/kg subcutaneously 3-5 min before hypoxia) intensifies an adaptive increase of aspartate aminotransferase activity and removes a decrease of alanine aminotransferase activity. Under these conditions stimulating effect of pyridoxal-5'-phosphate on transaminases activity in vitro weakens. A simultaneous administration of vitamin-coenzyme complex (thiamine pyrophosphate, lipoate, sodium 4-phospho-pantothenate, flavin-mononucleotide, nicotinate) intensifies these metabolic shifts and protective action of L-aspartate.

Alanine Transaminase↗
PubMed2004

Cysteine-321 of human brain GABA transaminase is involved in intersubunit cross-linking.

Gamma-aminobutyrate transaminase (GABA-T), a key homodimeric enzyme of the GABA shunt, converts the major inhibitory neurotransmitter GABA to succinic semialdehyde. We previously overexpressed, purified and characterized human brain GABA-T. To identify the structural and functional roles of the cysteinyl residue at position 321, we constructed various GABA-T mutants by site-directed mutagenesis. The purified wild type GABA-T enzyme was enzymatically active, whereas the mutant enzymes were inactive. Reaction of 1.5 sulfhydryl groups per wild type dimer with 5,5 cent-dithiobis-2-nitrobenzoic acid (DTNB) produced about 95% loss of activity. No reactive -SH groups were detected in the mutant enzymes. Wild type GABA-T, but not the mutants, existed as an oligomeric species of Mr = 100,000 that was dissociable by 2-mercaptoethanol. These results suggest that the Cys321 residue is essential for the catalytic function of GABA-T, and that it is involved in the formation of a disulfide link between two monomers of human brain GABA-T.

4-Aminobutyrate Transaminase↗
PubMed2004

Site-directed mutagenesis of human brain GABA transaminase: lysine-357 is involved in cofactor binding at the active site.

gamma-Aminobutyrate transaminase (GABA-T), a key enzyme of the GABA shunt, converts the major inhibitory neurotransmitter, GABA, to succinic semialdehyde. Although GABA-T is a pivotal factor implicated in the pathogenesis of various neurological disorders, its function remains to be elucidated. In an effort to clarify the structural and functional roles of specific lysyl residue in human brain GABA-T, we constructed human brain GABA-T mutants, in which the lysyl residue at position 357 was mutated to various amino acids including asparagine (K357N). The purified mutant GABA-T enzymes displayed neither catalytic activity nor absorption bands at 330 and 415 nm that are characteristic of pyridoxal-5'-phosphate (PLP) covalently linked to the protein. The wild type apoenzyme reconstituted with exogenous PLP had catalytic activity, while the mutant apoenzymes did not. These results indicate that lysine 357 is essential for catalytic function, and is involved in binding PLP at the active site.

4-Aminobutyrate Transaminase↗
PubMed1992

[Ischemic hepatitis. Important differential diagnosis of increased levels of transaminases in the liver].

In patients with pathological findings in tests of liver function, ischemic hepatitis is an important differential diagnosis. This condition is most often seen in patients with coronary heart disease. Acute circulatory failure may induce reduced liver perfusion with extreme elevation in transaminase levels within three to five days. The values return to normal within five to ten days and in uncomplicated cases there is minimal cholestasis. Ischemic hepatitis may progress to fulminant hepatic failure. The diagnosis can be made by clinical examination and biochemical tests alone. Biopsy gives a characteristic picture of centrilobular liver cell necrosis which confirms the diagnosis, but is seldom necessary.

Aged↗
PubMedDate not supplied

[Androgen participation in realizing the action of hydrocortisone and insulin on tyrosine-alpha-ketoglutarate transaminase synthesis in rat liver mitochondria].

Castration of adult rats did not distinctly alter the tyrosine alpha-ketoglutarate transaminase activity in liver tissue mitochondria. Administration of hydrocortisone caused the more pronounced increased of the tyrosine alpha-ketoglutarate transaminae activity in liver tissue mitochondria of young males as compared with the adult intact rats. Castration of adult rats did no alter stimulating effect of the glucocorticoid. Insulin decreased the stimulating effect of hydrocortisone on the synthesis of the synthesis of the enzyme in liver tissue mitochondria of young and adult castrated males. Insulin decreased the effect of hydrocortisone in adult castrated rats, provided with excess of testosterone propionate and did not change the effect in adul intact animals.

Age Factors↗
PubMed2006

[Relation of serological markers of hepatitis B virus and alanine transaminase to hepatic tissue pathology in patients with chronic hepatitis B].

OBJECTIVE: To investigate the association of serological markers of hepatitis B virus (HBV) and alanine transaminase (ALT) with hepatic tissue pathology in patients with chronic hepatitis B. METHODS: The serological marker of HBV, liver function and liver biopsy of 133 patients with chronic hepatitis B were measured and evaluated. The patients were divided into 4 groups according to HBeAg and HBV DNA positivity. Hepatic necrosis/inflammation grade and hepatic fibrosis were compared between the groups. RESULTS: Hepatic histological examination of all these patients showed inflammation, necrosis and different degrees of fibrosis. In patients with normal serum ALT, liver biopsy showed different degrees of inflammation, hepatic fibrosis, and even hepatocirrhosis. In patients with abnormal serum ALT negative for HBeAg, hepatic tissue inflammation and fibrosis were more serious. Hepatic tissue pathology was not paralleled with the level of HBV replication. CONCLUSION: Evaluation of the liver disease can not depend solely on serum ALT and viral loading in these patients. Hepatic tissue pathology in patients with chronic hepatitis B should be served as the most reliable evidence for evaluating hepatitis conditions and making the decision on antiviral therapy.

Adolescent↗
PubMed2006

Recovery of phosphatase and transaminase activity of mercury intoxicated Mus musculus (Linn.) liver tissue by Tribulus terrestris (Linn.) (Zygophyllaceae) extract.

The efficacy of the methanolic fraction (MF) of Tribulus terrestris fruit extract on mercury intoxicated mice, Mus musculus has been studied. At a median-lethal dose of mercuric chloride (12.9 mg/kg body wt.) administration an enhanced level of glutamate oxaloacete transaminase (GOT), glutamate pyruvate transminase (GPT) and simultaneously decreased level of acid phosphatase (ACP) and alkaline phosphatase (ALT) activities were noticed in the liver. Due to the mercury toxicity the liver cells are damaged to cause the alterations in their enzymes. During the recovery period, all the enzymological parameters are restored to reach near normal level. The result suggested that the oral administration of MF of T. terrestris fruit extract has (6 mg/kg body wt.) provided protection against the mercuric chloride induced hepatic damage in the mice, M. musculus.

Acid Phosphatase↗
PubMed1991

Changes in GABA-immunoreactivity and GABA-transaminase activity in rat amygdaloid complex in aging.

The distribution of gamma-aminobutyric acid (GABA), gamma-aminobutyric acid-transaminase (GABA-T) and glial fibrillary acid protein (GFAP) in the amygdaloid complex of young adult (3-month old) and aged (26-month old) Wistar rats was compared by using histo- and immunohistochemical techniques. The study revealed a heterogeneous distribution of GABA-immunoreactive and GABA-T positive nerve cells, fibers and terminals in various amygdaloid nuclei of young adult rats. A significant reduction in the density of GABA-immunoreactive neurons was demonstrated in the amygdala of aged rats. Reduced density and staining of GABA- and GABA-T-positive fibers and terminals were also seen in aged rat amygdala. Heavily GABA- and GABA-T-stained aberrant fibers and coarse puncta were clustered around blood vessels as well as under the pial and ependymal surfaces. GFAP-immunostaining demonstrated numerous hypertrophic astrocytes in these areas.

4-Aminobutyrate Transaminase↗
PubMedDate not supplied

[The effect of hydrocortisone and insulin on the activity and isoenzyme of tyrosine-alpha-ketoglutarate transaminase in cytostructures of rat liver].

Single administration of hydrocortisone or insulin into rats (body weight 200 g) and also combined treatment of the animals with the hormones at large doses caused a distinct increase in activities of anode and cathode isoenzymes of tyrosine-alpha-ketoglutarate transaminase in soluble fraction; total activity of the enzyme was also increased in mitochondria of rat liver tissue.

Animals↗
PubMedDate not supplied

[Glutamate decarboxylase and GABA transaminase activity in the mitochondrial fraction of the dog brain limbic system during postnatal development].

Overall glutamate decarboxylase (GDCase) activity in the initial mitochondrial fraction of the limbic structure is found to be regionally different it increases from the moment of birth up to 1 year, the midbrain reticular formation (RF), where the enzyme activity in the mitochondrial decreases in pups aged 3 month and reincreases in 1 year old dogs being the exception. Overall GABA-transaminase (GABA-T-ase) activity reaches the "adult" level and is the highest: in the hypothalamic and hippocampal mitochondria on the 1st postnatal day; in the limbic cortex (l1 and l2 fields), amygdala and midbrain RF--on the 12-16th postnatal days. During the period from 12-16 postnatal days up to the age of 1 year GABA-T-ase activity in the dog limbic system decreases reliably.

4-Aminobutyrate Transaminase↗
PubMed1977

Isozyme patterns of branched-chain amino acid transaminase in human tissues and tumors.

The isozymes (enzymes I and III) of branched-chain amino acid transaminase (EC 2.6.1.42) from various human tissues were separated by DEAE-cellulose column chromatography. Their distributions were found to be considerably different from those in rat tissues reported before. In rats, all tissues examined contained enzyme I and in addition enzyme II was found in the liver and enzyme III in the brain, ovary, and placenta. In humans, however, enzyme II was not found in any tissues examined including the liver, and enzyme III was found in many other tissues besides brain, ovary, and placenta. All normal human tissues except the lung, ovary, and brain contain less enzyme III than enzyme I. Various human cancers of the liver, kidney, stomach, pancreas, and uterus showed significantly higher ratios of enzyme III to enzyme I than those of the corresponding normal tissues. Fetal liver and kidney also contained much higher concentrations of enzyme III than adult liver and kidney. These findings suggest that change of the isozyme pattern of this enzyme in cancer is similar in humans and rats, and that cancer tissues tend to express more immature phenotypes than normal tissues. Enzymes I and III of human tissues showed the same substrate specificities for valine, leucine, and isoleucine, and these amino acids competed for the active site of the enzyme. Thus the hereditary diseases, hypervalinemia and hyperisoleucine-leucinemia, may be due to genetic alteration of the enzyme protein, resulting in change of its substrate specificity.

Animals↗
PubMedDate not supplied

[Tyrosine-alpha-ketoglutarate transaminase activity in the rat liver after partial hepatectomy and CCl4 poisoning].

Acitivity of tyrosine-alpha-ketoglutarate transaminase and induction of the enzyme by hydro cortisone were studied in rat liver tissue after partial hepatectomy and intoxication with CCl4 Administration of the hormone increased the enzymatic activity within 72 hrs after treatment with CCl4 but did not affect its value within 8 and 24 hrs. Activation of the enzyme by hydrocortisone correlated with the increased enzymatic activity observed within 20 hrs after partial hepatectomy. Possible mechanisms for activation of the enzyme, caused by endo- and exogenous factors, are discussed.

Animals↗
PubMed1979

The development and significance of transaminases and 5(1)-nucleotidase (5(1)-ribonucleotide phosphohydrolase) in chick testis.

The development of testicular glutamate oxaloacetate (GOT) and glutamate pyruvate (GPT) transaminases and of 5'-Nucleotidase was monitored in the male Nigerian fowl. The findings indicated triphasic and monophasic oscillations of GOT and GPT respectively with age. 5(1)-Nucleotidase was found to decrease with increase in the chronological age of the chicks. Furthermore, while GOT and GPT exhibited cubic and quadratic relationships respectively with age and testicular weights, 5(1)-Nucleotidase was related to both variables in a quadratic manner. The results are discussed in terms of spermatogenesis which may bear profoundly on the overall reproductive performance traits of the Nigerian cockerel.

Aging↗
PubMedDate not supplied

[Activity of various oxidases and transaminases in the rat liver in the readaptation period after hypokinesia up to 30 days].

The activity of alpha-ketoglutarate dehydrogenase and succinic dehydrogenase in readaptation after 15-day hypokinesia was within normal limits, whereas following 30-day hypokinesia it was enhanced on days 11-15. Pyruvate dehydrogenase exhibited hyperactivity in the end of readaptation week 2 both in 15- and 30-day hypokinesia which resulted in rat liver hyperactivity of glutamate dehydrogenase and transaminases. Normal levels of the latter were recorded on readaptation day 12-19.

Adaptation, Physiological↗
PubMed1990

Light microscope study of the enzymatic activities of aspartate aminotransferase, GABA transaminase and acetylcholinesterase in the mesencephalic trigeminal nucleus neural complex of Mauremys caspica.

The enzymatic activities of aspartate aminotransferase, GABA-transaminase and acetylcholinesterase were studied by means of histochemical methods in the mesencephalic trigeminal nucleus (MTN) neural complex of the turtle Mauremys caspica. Light microscope observations have demonstrated that MTN neurons have a positive reaction for these enzymes.

4-Aminobutyrate Transaminase↗