Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.5.1.4 (deaminase)
5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Microsomal AMP-deaminase was solubilized by 0.5 M KCl after treatment of microsomal membranes with 0.12 M KCl. Using disc-electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate one major protein component (mol. weight about 90 000) and three minor ones with molecular weights of 110 000, 80 000, and 60 000 were found in the soluble fraction. In addition to proteins, the fraction was found in the soluble fraction. In addition to proteins, the fraction was found to contain a small amount of phospholipids. The deaminase found in the solution may be reconstructed into the membranes at a decrease in KCl concentration, part of enzyme being bound in the inactive form under excess of the soluble fraction. Deaminase binding to the membranes is unaffected by the changes within the pH range of 6.2--7.8 and temperature range of 4--10 degrees C. It is assumed that AMP-deaminase is bound to other membrane components by electrostatic bonds.
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PMID:[Solubilization and reconstruction of microsomal AMP-deaminase from skeletal muscles]. 2 Jan 65

Iproniazid (1-isonicotinoyl-2-isopropylhydrazine), an antidepressant drug removed from clinical use because of hepatic injury, and isopropylhydrazine, a metabolite of iproniazid, were found to be potent hepatotoxins in rats. This animal model was used in studies in vivo and in vitro to define better the biochemical and chemical mechanism(s) by which iproniazid and isopropylhydrazine mediate hepatotoxicity. Phenobarbital, an inducer of a class of hepatic microsomal cytochrome P-450 enzymes, greatly potentiated the necrosis, whereas inhibitors of these microsomal enzymes such as cobalt chloride, piperonyl butoxide and alpha-naphthylisothiocyanate, prevented the necrosis. Bis-para-nitrophenyl phosphate, an inhibitor of esterase and amidase enzymes, prevented the necrosis caused by iproniazid but had no effect on the necrosis caused by isopropylhydrazine. Iproniazid and isopropylhydrazine labeled with tritium or carbon-14 in the isopropyl group were found to bind covalently to hepatic tissue macromolecules, and those pretreatments that increased hepatic necrosis significantly increased covalent binding, whereas those pretreatments which prevented necrosis significantly decreased covalent binding. Iproniazid labeled with tritium in the pyridine ring or carbon-14 in the carbonyl group did not bind significantly to hepatic tissue. Rats that were given iproniazid or isopropylhydrazine, labeled specifically with tritium and carbon-14 on the c-2 methine position of the isopropyl group, expired acetone and carbon dioxide labeled with carbon-14. More importantly, propane was expired and contained a ratio of 3H/14C that was identical to that in the administered iproniazid or isopropylhydrazine and also identical to the 3H/14C ratio of the metabolite that was covalently bound to hepatic tissue macromolecules. Experiments carried out with rat liver microsomes and isopropylhydrazine specifically labeled with deuterium, tritium and carbon-14 support the view that isopropylhydrazine is the metabolite of iproniazid that is oxidized by a microsomal P-450 enzyme to a species that alkylates tissue macromolecules. Some of the urinary metabolites excreted by rats that were administered hepatotoxic doses of iproniazid and isopropylhydrazine have been identified by cochromatography and isotope dilution with synthetic standards and by comparative mass spectra. Compounds excreted into the urine of rats dosed with iproniazid include iproniazid, iproniazid-1-oxide, isonicotinic acid, isonicotinoyl glycine, acetylisoniazid, isopropylhydrazine, 1-acetyl-2-isopropylhydrazine and acetone. Isopropylhydrazine, 1-acetyl-2-isopropylhydrazine, and acetone have been found in the urine of animals administered toxic doses of isopropylhydrazine.
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PMID:Hepatotoxicity and metabolism of iproniazid and isopropylhydrazine. 70 22

The metabolism of fungicide benzoic acid, 1,3-dithiolan-2-ylidenehydrazied (Yekuling) was studied quantitatively in rat liver microsomes and liver soluble fractions pretreated with phenobarbital (PB) and 3-methylcholanthrene (3-MC) by high pressure liquid chromatography. The experimental results indicated that the major metabolic pathway of Yekuling in vitro was hydrolysis. PB can enhance amidase activity to increase formation of benzoic acid and 1,3-dithiolan-2-ylidenehydrazine. 3-MC treatment elevated rat liver microsomal cytochrome P-448, enhancing S-oxidation of Yekuling. On the other hand, S-oxidation of Yekuling by rat liver microsomal MFO was NADPH-dependent.
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PMID:[Studies on metabolism of fungicide benzoic acid, 1,3-dithiolan-2-ylidenehydrazide in vitro]. 130 96

1. The initial slopes of the substrate-activity curves of several hydrolases were determined in the microsomal and cytosolic fractions of the liver of several fish recommended by OECD for the regulatory testing of chemicals. 2. Inter-species differences ranged within a factor of 7-17 for the esterases and reached a factor of 60 for the amidase. Guppy and carp appeared endowed with hydrolase activities which, overall, are much higher than zebra fish, trout and golden orfe. 3. The comparison with the rat liver microsomal hydrolases strongly suggests that fish are endowed with similar or higher levels of A-esterase and with much less B-esterase/amidase activities.
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PMID:Xenobiotic-metabolizing enzyme systems in test fish--IV. Comparative studies of liver microsomal and cytosolic hydrolases. 135 Sep 56

Methemoglobinemia produced by exposure to the herbicide propanil (3,4-dichloropropionanilide) is thought to be mediated by toxic metabolites formed during the hepatic clearance of the parent compound. We examined the metabolism of propanil and 3,4-dichloroaniline in rat liver microsomes to identify metabolites that may be involved in propanil-induced methemoglobinemia. The major pathway of propanil metabolism in microsomal incubations was acylamidase-catalyzed hydrolysis to 3,4-dichloroaniline. The reaction did not require NADPH, and was inhibited by the acylamidase inhibitors paraoxon and sodium fluoride. Oxidized metabolites were isolated by high-performance liquid chromatography, and identified as 2'-hydroxypropanil and 6-hydroxypropanil by comparison of their mass and nuclear magnetic resonance spectra to those of synthetic standards. Major microsomal metabolites of 3,4-dichloroaniline were 6-hydroxy-3,4-dichloroaniline and N-hydroxy-3,4-dichloroaniline. Both N-hydroxy-3,4-dichloroaniline and 6-hydroxy-3,4-dichloroaniline directly oxidized hemoglobin in rat erythrocyte suspensions in a concentration-dependent manner; however, the potency of N-hydroxy-3,4-dichloroaniline was at least an order of magnitude greater than that of 6-hydroxy-3,4-dichloroaniline.
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PMID:Metabolism of the arylamide herbicide propanil. I. Microsomal metabolism and in vitro methemoglobinemia. 231 34

By the use of spin trapping agents phenyl-t-butyl nitrone (PBN) and 4-pyridyl-1-oxide-t-butyl nitrone (4-POBN) free radical species were detected in isolated hepatocytes incubated with either isoniazid, iproniazid and their respective metabolites acetyl-hydrazine and isopropyl-hydrazine. The addition of bis-nitrophenyl phosphate, an inhibitor of the acylamidase enzymes, to isolated hepatocytes decreased the free radical activation of isoniazid and iproniazid, but not that of acetyl- and isopropyl-hydrazine, confirming that the radical species were originating from the biotransformation of these latter compounds. The ESR spectra were ascribed to the trapping of, respectively, acetyl and isopropyl free radicals on the basis of the analogies of the spectral feature with those of chemically-prepared spin adducts. Comparable ESR spectra were also observed during the metabolism of acetyl- and isopropyl-hydrazines by liver microsomes and their formation was inhibited by the omission of NADP+, anaerobic incubation and enzyme denaturation. In the microsomal preparations inhibitors of the mixed function oxidase system decreased to various extents the free radical formation and a similar effect was also observed following the destruction of cytochrome P-450 induced by pretreating the rats with CoCl2. The addition of reduced glutathione also decreased the radical trapping indicating that GSH can effectively compete with the spin traps for the reaction with the free radicals. The incubation of isolated hepatocytes with isoniazid or acetyl-hydrazine reduced by 20-25% the intracellular GSH content, while a 50% decrease in GSH was present in the cells exposed to iproniazid and isopropyl-hydrazine. In the same hepatocyte preparations stimulation of lipid peroxidation and leakage of LDH were also observed during cell incubation with iproniazid and isopropyl-hydrazine, but not with isoniazid or acetyl-hydrazine and the extent of both phenomena correlated with the susceptibility of the above compounds to the free radical activation.
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PMID:Spin trapping of free radical intermediates produced during the metabolism of isoniazid and iproniazid in isolated hepatocytes. 282 Apr 25

Deacetylation of N-hydroxy-2-acetylaminofluorene (N-hydroxy-AAF) to N-hydroxy-2-aminofluorene (N-hydroxy-AF) has been proposed as one of the critical metabolic steps in the formation of hepatic DNA adducts and the initiation of liver tumors in 12-day-old male B6C3F1 mice. In this study, the importance of the microsomal deacetylase activity for N-hydroxy-AAF in the initiation of hepatocarcinogenesis in these mice was demonstrated by using a carboxylesterase and amidase inhibitor, bis(p-nitrophenyl)phosphate (BNPP), that is much less toxic in vivo than is paraoxon. Pre-incubation of liver microsomes from 12-day-old male B6C3F1 mice with 10(-3) M BNPP reduced the deacetylase activity by 80% while paraoxon inhibited the deacetylase activity completely at a concentration of 10(-4) M. Pretreatment of 12-day-old male B6C3F1 mice with 4 X 75 micrograms doses of BNPP/g body weight before the administration of N-hydroxy-AAF reduced the hepatic N-(dGuo-8-yl)-AF adduct levels to 1.09 and 0.68 pmol/mg DNA compared with 2.87 and 1.64 pmol/mg DNA for mice treated once with 0.06 or 0.03 mumol of N-hydroxy-AAF/g body weight respectively. However, BNPP pretreatments did not affect the levels of the acetylated DNA adducts, N-(dGuo-8-yl)-AAF and 3-(dGuo-N2-yl)-AAF, formed by these doses of N-hydroxy-AAF. The initiation of liver tumors by N-hydroxy-AAF was also inhibited by BNPP pretreatment. Thus, for mice that received single doses of 0.12, 0.06 and 0.03 mumol of N-hydroxy-AAF/g body weight, the multiplicities of liver tumors at 10 months were reduced by BNPP pretreatments to 5.6, 1.0 and 0.3 compared with multiplicities of 11.8, 4.8 and 1.7 without pretreatment respectively. On the other hand, BNPP pretreatments had no significant inhibitory effects on the levels of the hepatic DNA-N-(dGuo-8-yl)-AF adduct or on the liver tumor multiplicities induced by comparable doses of N-hydroxy-AF. It is concluded that deacetylation of N-hydroxy-AAF to N-hydroxy-AF is essential for the metabolic activation, DNA-N-(dGuo-8-yl)-AF adduct formation and liver tumor initiation in infant male B6C3F1 mice by N-hydroxy-AAF.
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PMID:The essential role of microsomal deacetylase activity in the metabolic activation, DNA-(deoxyguanosin-8-yl)-2-aminofluorene adduct formation and initiation of liver tumors by N-hydroxy-2-acetylaminofluorene in the livers of infant male B6C3F1 mice. 338 46

alpha-Bromoisovalerylurea (BIU) is used as model substrate for studies on the pharmacokinetics of glutathione conjugation in vivo. Its metabolism in isolated rat hepatocytes is presently studied. A major part of the substrate was conjugated with glutathione, but also amidase-catalyzed hydrolysis occurred, resulting in the products urea and alpha-bromoisovaleric acid (BI). The amidase activity was located in the microsomal fraction of the rat liver. The product of hydrolysis, BI, also was conjugated efficiently with glutathione. In glutathione-depleted hepatocytes, no glutathione conjugates but only urea and BI were formed. A pronounced stereoselectivity in the metabolism of the BIU enantiomers was observed: (R)-BIU was conjugated with glutathione much faster than (S)-BIU. (S)-BIU was hydrolyzed substantially in the cells and the glutathione conjugate of the hydrolytic product, (S)-BI, could be detected. At high BIU concentrations (500 microM of the racemate) intracellular glutathione was seriously depleted; then, the cosubstrate availability most likely was the rate-limiting factor in the conjugation of BIU with glutathione. More urea was formed from (racemic) BIU in isolated rat hepatocytes in the present study than in the perfused liver and the intact rat in previous studies. This in vivo-in vitro difference is tentatively assigned to differences in glutathione availability in these systems. The results suggest that BI may also be a useful model substrate to study the kinetics of glutathione conjugation in vivo and in vitro.
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PMID:Stereoselective glutathione conjugation and amidase-catalyzed hydrolysis of alpha-bromoisovalerylurea enantiomers in isolated rat hepatocytes. 366 62

Porphorbilinogen oxygenase (EC 4.2.1.24) was associated with the microsomal fraction of bone marrow in normal rats and in rats submitted to erythropoietic stress, while porphobilinogen deaminase (EC 4.3.1.8) of the same origin was present in the cytosol. An NADPH-dependent electron-donor system for the oxygenase was also present in the microsomes of the bone marrow. Under conditions of erythropoietic stress caused by hypoxia, the activities of both enzymes were found to be inversely correlated. While the oxygenase showed minimum activity between the 4th and 8th day of hypoxia, porphobilinogen deaminase reached its maximum activity during this period. After the 8th day of hypoxia, oxygenase activity increased while deaminase activity decreased. The NADPH-dependent electron-transport system necessary for the microsomal oxygenase activity was largely inactivated after the 10th day of hypoxia, while oxygenase activity was not affected. The particulate porphobilinogen oxygenase could be solubilized from the bone marrow microsomes with 1% deoxycholate or 0.5 M KCl. In addition, the oxygenase was also released by freezing and thawing the microsomes isolated from bone marrow of rats which had been submitted to an erythropoietic stress (hypoxia or phenylhydrazine). The enzyme solubilized with deoxycholate or KCl showed a high molecular weight form and a low molecular weight form (Mr 25 000). The former could be transformed into the latter either by treatment with 2 M KCl or by succinylation. When the oxygenase was solubilized by freezing and thawing a third molecular weight form (Mr 50 000) also appeared. The solubilized enzyme could be succinylated without loss of its catalytic activity, while the membrane-bound enzyme could not be succinylated.
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PMID:The regulation of porphobilinogen oxygenase and porphobilinogen deaminase activities in rat bone marrow under conditions of erythropoietic stress. 369 63

Both iproniazid and isopropylhydrazine were metabolized to the hydrocarbon products, propane and propylene, with nearly identical Michaelis constants and rates. This reaction appeared to be catalyzed by microsomal cytochrome P-450. Isonicotinic acid, a product of iproniazid hydrolysis by various amidases, was produced in only very small quantities, suggesting that the other amidase product, isopropylhydrazine, may not be an obligatory intermediate in the pathway of hydrocarbon formation from iproniazid. Hydrocarbon formation from iproniazid was more sensitive to inhibition in vitro by bis-p-nitrophenylphosphate (used in vivo as an amidase inhibitor) than was isopropylhydrazine. Iproniazid must be directly metabolized by cytochrome P-450 to yield propane and propylene, presumably via an azo ester intermediate which could give rise to an isopropyl radical, the chemical species presumed to be responsible for the hepatoxicity apparent after administration of large doses of iproniazid in vivo.
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PMID:Propane and propylene formation during the microsomal metabolism of iproniazid and isopropylhydrazine. 397 3


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