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At least 19 recordsLinked to original sources
PubMed1975

Covalently bound FAD in d-6-hydroxynicotine oxidase. Immunological studies of D- and L-6-hydroxynicotine oxidase: evidence for a D-enzyme precursor.

Antersera prepared against both enantiozymes, D- and L-6-hydroxynicotine oxidase, formed precipitins in double diffusion tests with their respective antigens only. A mixture of the two antisera caused spur formation of the two precipitin lines obtained with the pure enzymes. Antiserum to L-apoprotein reacted with native L-enzyme and L-apoprotein but not with the D-sspecific enzyme. D-6-hydroxynicotine oxidase activity was inhibited by the anti-D-antiserum, leaving the L-enzyme fully active, while anti-L-antiserum inhibited the L- but not the D-specific activity. The delayed induction of D-6-hydroxynicotine oxidase as compared to the other activities of the nicotine-degrading sequence and the differential immunochemical behavior of the enantiozymes allowed the search for a D-enzyme precursor. In cells harvested 3 hours after the addition of DL-nicotine, the L-enzyme activity was present, whereas no D-enzyme activity could be detected. However, an extract of these cells did form an immunoprecipitin line with anti-D-antiserum. L-6-Hydroxynicotine oxidase, but no D-6-hydroxynicotine oxidase activity, could also be induced in Arthrobacter oxidans grown in a medium with a high glucose content and DL-nicotine as the sole nitrogen source. An extract of these L-induced cells produced the specific immunoprecipitation with anti-D-antiserum. A pulse-chase experiment with cells grown first on glucose and DL-nicotine in the presence of [14C]leucine and then in an unlabeled medium which induces D-6-hydroxynicotine oxidase activity resulted in a radioactive D-enzyme-immunoprecipitin line. From these experiments it is concluded that a precursor of the active D-enzyme is induced simultaneously with the other nicotine-degrading enzymes.

Arthrobacter↗
PubMed1975

Catalytically inactive sucrase antigen of rabbit small intestine: the enzyme precursor.

By immunofluorescence microscopy using a specific antibody to the active rabbit sucrase-isomaltase complex, a catalytically inactive sucrase antigen was discovered on the small intestinal mucosa of young rabbits still lacking sucrase activity. In adult rabbits, the same antigen was demonstrated on enterocytes of mucosal crypts devoid of sucrase. Catalytically inactive antigen was isolated by means of immobilized antibody to active sucrase, and it was compared with the active sucrase-isomaltase complex. From structural similarities between the 2 proteins and from the fact that active sucrase succeeds the inactive antigen in both the maturing and the mature rabbit, it is concluded that the inactive antigen is the enzyme precursor. In some patients with hereditary sucrase-isomaltase deficiency, abnormal persistence of sucrase precurosr due to a faulty activation mechanism may be the underlying defect.

Age Factors↗
PubMed1975

The proteolytic proenzymes in the peritoneal exudate during acute experimental pancreatitis of the rat.

Precursors of proteolytic enzymes were demonstrated in the peritoneal inflammatory exudate during acute experimental pancreatitis of the rat. This was done by separating the proteinase inhibitors and proenzymes by gel filtration on Sephadex G-200. After elution the proenzymes could be demonstrated by activating them with enterokinase or with trypsin. The proenzymes were eluted after the main protein bulk and proteinase inhibitors. Enzyme precursors were absent from the exudate of formalin-induced peritonitis, which suggests that the proenzymes present in the exudate of pancreatitis are of pancreatic origin. The demonstration of proenzymes in perripheral blood during pancreatitis was tested with the several modifications of the same methods, but the results were not convincing, probably owing to the insensitivity of the methods used.

Acute Disease↗
PubMed1977

Changes in the collagenolytic activity released by primary VX-2 carcinoma cultures as a function of tumor growth.

Serum-free media of minced tissue cultures of VX-2 rabbit carcinoma contained a specific collagenolytic activity capable of releasing soluble radioactive peptides from [14C]-labeled collagen fibrils. It was also capable of reducing the viscosity of acid-soluble collagen solutions by cleaving the tropocollagen (TC) molecules primarily at one site to TCA (75%) and TCB (25%) fragments. Three chromatographic fractions were separated by gel filtration: F1, (MW 85-110,000) present in larger amounts in early cultures of younger tumor tissue; F2, (MW-35-40,000) the major component with maximum production in the day 3 media of younger and advanced tumor tissues; F3, (MW 18-22,000) the minor component. Early cultures of younger tumor tissue contained a latent collagenase and were subject to trypsin activation suggesting the presence of inactive enzyme precursors or an enzyme-inhibitor complex.

Animals↗
PubMed1976

Regulation of penicillin acylase in Escherichia coli by cyclic AMP.

1. Cyclic AMP was found to stimulate penicillin acylase activity. 2. It also overcame the repression of glucose and restored enzyme synthesis to the non-repressed levels. 3. The conversion of inactive enzyme precursor into active enzyme was not stimulated by cyclic AMP in cells in which protein synthesis was inhibited by chloramphenicol. 4. Cyclic AMP failed to stimulate enzyme production in cells in which messenger RNA synthesis was arrested by rifampicin or inducer removal. 5. Cyclic AMP appears to participate in the regulation of this enzyme at the transcriptional level.

Amidohydrolases↗
PubMed1979

[Metabolic characteristics of prolyl hydroxylase].

The turnover time of prolyl hydroxylase in the skin of one-day-old rats treated in vivo with L-[14C]leucine is 22--34 hrs. Theoretically this time interval comprises two processes: i. e. incorporation of [14C]-Leu into the inactive enzyme precursor and transformation of the inactive from into the active enzyme.

Animals↗
PubMed1992

A complementary DNA for human choline acetyltransferase induces two forms of enzyme with different molecular weights in cultured cells.

Complementary DNA (cDNA) clones containing the entire coding region of human choline acetyltransferase (ChAT) were isolated from cDNA libraries prepared from the autopsied spinal cord. In the human cDNA, the ATG codon assigned to the putative initiation codon for pig, rat and mouse ChAT cDNAs was replaced by ACG. The human cDNA contained an in-frame ATG codon 324 nucleotides upstream of the ACG codon. Therefore, human ChAT cDNA should code for a 748 amino acid polypeptide of 82.6 kDa. This deduced molecular weight was larger than that of ChAT protein purified from the human brain and placenta (64-70 kDa). The human ChAT cDNA containing the entire coding region was ligated to an expression vector and introduced into African green monkey kidney (COS) cells and Chinese hamster ovary (CHO) cells. The cells expressed high ChAT activity and produced two protein bands immunostained with an antibody to monkey ChAT. The molecular weight of the proteins was estimated to be approximately 70 and 80 kDa by polyacrylamide-SDS gel electrophoresis. When partial cDNAs that lacked the first ATG but contained the replaced ACG codon were introduced into COS cells, the cells expressed moderate ChAT activity and an immunoreactive protein band of 70 kDa. These results indicate that translation of human ChAT mRNA starts at two sites and produces two enzyme proteins with different molecular weights. It might be that the larger form of ChAT molecule is an enzyme precursor for processing or that the N-terminal extrapeptide is needed for subcellular localization of the enzyme.

Amino Acid Sequence↗
PubMed1976

The localization of enzymes in tissue sections by immuno-histochemistry. Conventional antibody and mixed aggregation techniques.

Methods for detecting enzymes in tissue sections by antibody techniques are reviewed. In all these techniques, sections are first incubated with antibody. The bound antibody is visualized in one of four ways: identifying a label such as fluorescein linked to the antibody; using a labelled anti-antibody; employing complement and labelled anti-complement; or making use of a mixed aggregation immuno-cytochemical method. The last technique consists of three steps. A section is first incubated with antiserum, and secondly with the soluble enzyme under investigation. Thirdly the desired enzyme is "stained" using a conventional cytochemical method. The method is specific since, for example, the soluble enzyme used in the second step can bind only to antigenic determinants which are identical to those of the enzyme localized in the tissue. Thus purification of antigen and antibody sources is simplified, and chemical modifications of the antigen and antibody are avoided. Antibody also acts as a selective fixative for tissue antigen. It will inhibit the catalytic activity of its antigen and, in this way, permit the enzyme activity arising after the reaction of tissue enzyme-antibody complex with soluble enzyme to be amplified selectively. The mixed aggregation immuno-cytochemical technique has been used successfully with membrane-bound enzymes and cytoplasmic enzymes and for the demostration of catalytically inactive enzyme precursors.

Agglutination Tests↗
PubMed1979

Significance of the electrophoretic modifications of defective pyruvate kinase variants. Study of six new observations.

Six new defective pyruvate kinase variants have been characterized in patients suffering from chronic hemolysis. Partially purified enzyme variants exhibited various anomalies from immunological, kinetic, stability and electrophoretic points of view. The significance of the electrophoretic anomalies has been interpreted in view of the normal post-synthetic maturation of the precursor enzyme L'4 into L2L'2 and L4, and the ability of trypsin to induce in vitro the transition L'4 leads to L4 has been tested. One defective enzyme existed in a single L'4 form and could not be transformed by trypsin into L4. In three cases slow-moving L'4 and L2L'2 forms were transformed by trypsin into an abnormal slow-moving L4 form. In the last two observations the L'4 and L2L'2 forms exhibited normal mobility and were normally transformed by trypsin into L4. The relevance of these data to the functional anomalies of the defective variants and to the nature of the primary genetic anomaly giving rise to the congenital defects in erythrocyte pyruvate kinase is discussed.

Anemia, Hemolytic, Congenital↗
PubMed1992

Kininogenase of the aortic wall in spontaneously hypertensive rats.

We determined kinin-generating activity (kininogenase) in the thoracic aorta of spontaneously hypertensive rats (SHRs) at age 5 and 15 weeks and in appropriately age-matched Wistar-Kyoto (WKY) rats. Aorta homogenates were incubated with partially purified dog kininogen, and the resulting kinins were extracted with ethanol. The kinins were determined by a sensitive kinin radioimmunoassay (RIA). Kininogenase activity was expressed as mean +/- SEM, picogram kinin generated/mg x protein/h. Active kininogenase in SHR was approximately one-third in 5-week-old and about one-fifth in 15-week-old rats when compared with their normotensive controls. Total kininogenase activity in SHRs was approximately 80% and 58% of the normotensive controls at ages 5 weeks and 15 weeks, respectively. Active enzyme was 14% of the total in 5-week-old SHRs, and it was only 5% of the total in 15-week-old SHRs. It seems unlikely that the changes in kininogenase are secondary to hypertension because blood pressor is only marginally elevated at 5 weeks according to the literature. We hypothesize that genetic hypertensive rats may suffer from an inherent deficiency in the kininogenase activity of the vascular wall. The deficiency may also be in the mechanism of activation of precursor enzyme.

Aging↗
PubMed1975

Different secretory responses of periinsular and other acini in the rat pancreas after pilocarpine injection.

Histological, histochemical, and electron microscopical investigations of the rat pancreas, one to five hours after pilocarpine injection (4 mg in 1 ml normal saline solution), showed different secretory responses in periinsular and apoinsular acinar cells. The responsiveness to parasympathetic stimulation is markedly retarded and weakened in the periinsular area. It is supposed that the halo phenomenon is related not only to an inhibition of the secretion, but also to a longer lasting synthesis of zymogen granules. The insular hormones, glucagon and insulin, which are possibly locally enriched by insulo-acinar capillary anastomoses or by diffusion, may be involved in the regulation of activity in the periinsular cells.

Acid Phosphatase↗
PubMed1978

Relationship between subunit size and number of rare electrophoretic alleles in human enzymes.

Data from published sources were used to compare the numbers of different electrophoretic alleles of 29 monomeric and dimeric human enzymes to their respective subunit molecular weights. Only those human enzymes were considered for which the total sample sizes were in excess of 2000 individuals. Correlations between these two variables were determined within sample size ranges of 2000 less than or equal to n less than or equal to 3000 and 4000 less than or equal to n less than or equal to 5000 individuals, and separately by quaternary class. There was no statistically significant correlation observed for the smaller sample size range in monomers; however, the correlations for the larger sample size range in monomers and both ranges in dimers were significant. Since there is no relationship between subunit size and heterozygosity, the relationships are due primarily to the incidence of rare alleles. These findings demonstrate the effect of locus-specific mutation rates, expected as a consequence of variation of cistron sizes, and imply that other forces are responsible for the relative frequencies of common alleles at some of the loci.

Alleles↗
PubMed1979

Synthesis and degradation of xanthine dehydrogenase in chick liver. In vivo and in vitro studies.

The present study describes the (xanthine:NAD+ oxidoreductase, EC 1.2.1.37) synthesis and degradation of chick liver xanthine dehydrogenase in vivo and in organ cultures. The results indicate that control of xanthine dehydrogenase activity is mediated by changes in the rate of enzyme synthesis, but that degradation rates are unaffected. The results also suggest that xanthine dehydrogenase synthesis occurs through a previously unreported intermediate. Detected in cultures of liver tissue, this intermediate apparently is not converted into an active enzyme. A model of synthesis and degradation for xanthine dehydrogenase proposes that the synthesis of the enzyme is proportional to messenger RNA and includes an inactive enzyme precursor and a second inactive intermediate prior to degradation. Integrated mathematical solutions describing the concentration of intermediates as a function of time can be found explicitly for simple models. The appendix to this paper extrapolates solutions for one-, two- and three-step models to generate a mathematical solution for an 'n'-step model containing 'n' intermediates. The rate constants in the solutions can be found experimentally.

Animals↗
PubMed1975

Gene dosage effects in polyploid strains of Saccharomyces cerevisiae containing gua-1 wild-type and mutant alleles.

Triploid and tetraploid Saccharomyces strains containing different combinations of a gua-1 mutant allele and the corresponding wild type were prepared. The cultivation of the different strains in media upon which the mutant fails to grow leads to a pronounced growth rate response to the dosage of the wild-type allele. Proportionality between the specific activity of the guanosine 5'-monophosphate synthetase and the wild-type dosage was reavealed. Inosine 5'-monophosphate dehydrogenase, the precursor enzyme in the pathway, is derepressed in a sigmoid manner when the wild-type dosage is reduced, whereas the activity of cytosine deaminase, investigated as a reference enzyme, is less affected.

Alleles↗
PubMed1978

Intracellular serine protease of Bacillus subtilis: sequence homology with extracellular subtilisins.

Intracellular serine protease was isolated from stationary-grown Bacillus subtilis A-50 cells and purified to homogeneity. The molecular weight of the enzyme is 31,000 +/- 1,000, with an isoelectric point of 4.3. Its amino acid composition is characteristically enriched in glutamic acid content, differing from that of extra-cellular subtilisins. The enzyme is completely inhibited with phenylmethylsulfonyl fluoride and ethylenediaminetetraacetic acid. Intracellular protease possesses negligible activity towards bovine serum albumin and hemoglobin, but has 5- to 20-fold higher specific activity against p-nitroanilides of benzyloxycarbonyl tripeptides than subtilisin BPN'. Esterolytic activity of the enzyme is also higher than that of subtilisin BPN'. The enzyme is sequence homologous with secretory subtilisins throughout 50 determined NH2-terminal residues, indicating the presence of duplicated structural genes for serine proteases in the B. subtilis genome. The occurrence of two homologous genes in the cell might accelerate the evolution of serine protease not only by the loosening of selective constrainst, but also by creation of sequence variants by means of intragenic recombination. Three molecular forms of intracellular protease were found, two of them with NH2-terminal glutamic acid and one minor form, three residues longer, with asparagine as NH2 terminus. These data indicate the possible presence of an enzyme precursor proteolytically modified during cell growth.

Amino Acid Sequence↗