Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.1.22 (cystathionine beta-synthase)
 965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four enzymes necessary for the metabolism of methionine by the trans-sulfuration pathway, methionine adenosyltransferase (EC 2.5.1.6), adenosylhomocysteinase (EC 3.3.1.1), cystathionine beta-synthase (EC 4.2.1.22) and cystathionine gamma-lyase (EC 4.4.1.1) were identified in Tetrahymean pyriformis. The ability of these cells to transfer 35S from E135S]methionine to form [35S] cysteine was also observed and taken as direct evidence for the functional existence of this pathway in Tetrahymena. An intermediate in the pathway and an active methyl donor, S-adenosylmethionine, was qualitatively identified in Tetrahymena and its concentration was found to be greater in late stationary phase cells than in early stationary phase cells.
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PMID:The transsulfuration pathway in Tetrahymena pyriformis. 1 63

1. Methionine adenosyltransferase (ATP:L-methionine-S-adenosyl transferase, EC 2.5.1.6), cystathionine beta-synthase F1L-serine hydro-lyase (adding homocysteine), EC 4.2.1.22] and cystathionine gamma-lyase [L-cystathionine cysteine-lyase (deaminating), EC 4.4.1.1] activities were found only in the cytosol fraction of rat liver cells. None was found in the mitochondrial or endoplasmic reticulum fractions as judged by the distribution of marker enzymes on a density gradient after centrifugation of the cytoplasmic fraction of a liver homogenate, or in a preparation of liver cell nuclei. 2. Polymorphs, lymphocytes (with admixed monocytes) and mixed bone marrow white cells contained no methionine adenosyl transferase, cystathionine beta-synthase or cystathionine gamma-lyase activities. 3. The possible bearing of these results on the problem of abnormal cystine storage in cystinosis is briefly discussed.
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PMID:Methionine adenosyltransferase, cystathionine beta-synthase and cystathionine gamma-lyase activity of rat liver subcellular particles, human blood cells and mixed white cells from rat bone marrow. 105 81

The contents of the sulfur amino acids, and the activities of cystathionine beta-synthase and cystathionine gamma-lyase were measured in various regions of the brain and several other tissues in both normal mice and rolling mice Nagoya. The cystathionine content and cystathionine beta-synthase activity were found to be unevenly distributed in various regions of the brain in both normal mice and rolling mice Nagoya, being highest in the cerebellum. Except for the mesencephalon and thalamus plus hypothalamus, the cystathionine content and cystathionine beta-synthase activity in the brain regions of rolling mice Nagoya were much higher than those of the normal mice. The cystathionine content after D,L-propargylglycine treatment was also found to be unevenly distributed in various brain regions in both normal mice and rolling mice Nagoya. The concentrations of cystine and methionine were also higher in all regions of the brain of rolling mice Nagoya than those of normal mice, while the concentration of taurine in the various regions of the brain was almost the same in normal mice and rolling mice Nagoya. Cystathionine beta-synthase and cystathionine gamma-lyase activities in the liver, kidney, and pancreas were almost the same in both the normal mice and rolling mice Nagoya.
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PMID:Sulfur amino acid levels and related enzyme activities in various brain regions (and other tissues) in normal mice and rolling mice Nagoya. 148 34

Cystathionine was cleaved into 2-ketobutyric acid, cysteine and ammonia by cystathionase. 2-Ketobutyric acid was converted into 3-ethyl-2-hydroxy-6,7-dimethoxyquinoxaline (EHDQ) by reaction with 1,2-diamino-4,5-dimethoxybenzene. When EHDQ was measured in a mobile phase of pH 2.1 using high-performance liquid chromatography with ultraviolet detection, 250 pmol of L-cystathionine in 250 microliters of the reaction mixture could be determined. Because EHDQ has a strong fluorescence in a mobile phase of pH 6.5 at 447 nm, on excitation at 365 nm, as little as 2.5 pmol of cystathionine in 250 microliters of the reaction mixture could be determined by high-performance liquid chromatography with fluorimetric detection. Cystathionase activity was assayed on the basis of the same principle by determining cystathionine in as little as 63 ng of rat liver by fluorimetric detection. Cystathionine beta-synthase activity was measured by the same method by determining cystathionine formed in only 113 ng of wet weight of rat liver. Using these methods, both cystathionine beta- and gamma-lyase activities in Saccharomyces cerevisiae were determined, because quinoxaline derivatives from pyruvate and 2-ketobutyrate could be measured simultaneously by high-performance liquid chromatography.
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PMID:Sensitive determination of cystathionine and assays for cystathionine beta- and gamma-lyase, as well as cystathionine beta-synthase, using high-performance liquid chromatography. 162 86

Regulation of the two enzymes in reverse trans-sulfuration was investigated in Saccharomyces cerevisiae. In wild-type strains, cystathionine gamma-lyase, but not cystathionine beta-synthase, was depressed nearly 15-fold if cells were starved for both inorganic and organic sulfur compounds. In a met17 strain which is defective of O-acetylserine and O-acetylhomoserine sulfhydrylase, the same enzyme was derepressed if organic sulfur compounds were limited; the repressive effect was in the order of glutathione greater than methionine greater than cysteine. The repressive effect of methionine was not observed, however, in a cys2 cys4 strain which is deficient of serine O-acetyltransferase and cystathionine beta-synthase, indicating that methionine itself is not the effector. The weak repressive effect of cysteine was attributed to inefficient uptake of this amino acid. Our observations indicate that cystathionine gamma-lyase is the target of regulation in reverse trans-sulfuration and that cysteine is very likely to be the effector of this regulation.
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PMID:Regulation of cystathionine gamma-lyase in Saccharomyces cerevisiae. 178 5

We examined the change in glutathione metabolism in vitamin B-6-deficient rats. Vitamin B-6-deficient rats were fed a vitamin B-6-deficient diet containing 0.56% methionine and 0.075% cystine for 8 wk. Controls were fed an identical diet supplemented with 10 mg pyridoxine hydrochloride/kg diet. Glutathione concentrations in each organ examined were similar in control and vitamin B-6-deficient rats, and the values were comparably lower after intraperitoneal injection of diethylmaleate. However, buthionine sulfoximine caused a significantly greater decrease in glutathione levels in the liver and lungs of vitamin B-6-deficient rats relative to controls. Glutathione peroxidase activity in the liver of vitamin B-6-deficient rats was higher than in control animals; however, glutathione transferase activity in tissues other than liver of vitamin B-6-deficient rats was higher than in the controls. The activities of gamma-glutamyl-transferase in the liver and spleen of vitamin B-6-deficient rats were significantly lower than control values. The holoenzyme activities of cystathionine beta-synthase and cystathionine gamma-lyase in the liver of vitamin B-6-deficient rats were markedly reduced. These findings indicate that although the activities of enzymes that synthesize cysteine from methionine were decreased by vitamin B-6 deficiency, the level of synthesis and supply of cysteine in vitamin B-6-deficient rats were sufficient to maintain the same glutathione level as in controls, and that glutathione utilization in the liver was accelerated by vitamin B-6 deficiency.
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PMID:Glutathione levels and related enzyme activities in vitamin B-6-deficient rats fed a high methionine and low cystine diet. 188 Jun 14

A yeast strain highly resistant to propargylglycine (an inhibitor of cystathionine gamma-lyase) was isolated from air. It was partially characterized, but it has not been identified with any known yeast species. Its sulphur amino acid metabolism differed from that of other fungi by the lack of the reverse transsulphuration pathway from methionine to cysteine, as no activity of cystathionine beta-synthase or cystathionine gamma-lyase was found. The functional lack of this pathway was confirmed by growth tests and by experiments with [35S]methionine. In contrast to Saccharomyces cerevisiae neither homocysteine synthase nor the sulphate assimilation pathway were repressible by methionine in the new strain; on the contrary, a regulatory effect of cysteine was observed.
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PMID:A yeast with unusual sulphur amino acid metabolism. 207 24

The alleviation mechanism of methionine toxicity by dietary glycine was investigated in weanling rats fed a high-methionine diet. When rats were fed a 10% casein diet containing 2% methionine, the activities of methionine adenosyltransferase, cystathionine beta-synthase, and cystathionine gamma-lyase, which participate in the methionine metabolism in the transsulfuration pathway, were significantly enhanced. But the addition of 2% glycine to the high methionine diet did not cause further increase in these enzyme activities; the activities of methionine adenosyltransferase and cystathionine beta-synthase were rather decreased while cystathionine gamma-lyase activity was not altered. Methionine transaminase activity was essentially insensitive to the dietary addition of methionine and glycine. In rats fed a high methionine diet, the hepatic methionine level was significantly increased with a concomitant decrease in the levels of glycine, serine, and threonine. The addition of glycine to the high methionine diet effectively suppressed the enhancement of the hepatic methionine level and almost completely restored the glycine level, but it only partially restored the serine level and further decreased the threonine level. From these results, it is suggested that the alleviating effect of dietary glycine on methionine toxicity is primarily elicited by the restoration of the hepatic glycine level rather than by an increase in hepatic enzyme activity.
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PMID:Effect of dietary glycine on methionine metabolism in rats fed a high-methionine diet. 366

We have investigated selenocysteine (2-amino-3-hydroselenopropionic acid) synthesis with cystathionine beta-synthase (EC 4.2.1.22) and cystathionine gamma-lyase (EC 4.4.1.1) of rat liver. When selenohomocysteine and serine were incubated with cystathionine beta-synthase, selenocystathionine was formed at a rate of 69% of that of cystathionine synthesis. Cystathionine gamma-lyase catalyzed alpha, gamma elimination of selenocystathionine to yield alpha-ketobutyrate, selenocysteine, and NH3. The reaction rate was about 3 times higher than that of cystathionine elimination. Cystathionine beta-synthase, however, did not catalyze direct formation of selenocysteine from serine and H2Se. Thus, selenocysteine is synthesized from selenohomocysteine and cystathionine beta-synthase and cystathionine gamma-lyase reactions. We confirmed this synthetic pathway also with a mixture of both enzymes and with a homogenate of rat liver.
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PMID:Enzymatic synthesis of selenocysteine in rat liver. 645 63

Cystathionine beta-synthase, S-adenosylmethionine synthetase and cystathionase activities were assayed in skin fibroblast cultures from five pyridoxine responsive and five pyridoxine non-responsive homocystinurics, six obligate heterozygotes for homocystinuria and ten normal control subjects. The specific deficiency in cystathionine beta-synthase activity was confirmed in nine of the homocystinuric cultures. However, in one pyridoxine responsive case the level of cystathionine beta-synthase activity was found to be comparable with those of the heterozygotes. A negative correlation appeared to exist between the level of residual enzyme activity and the pre-treatment severity of clinical symptoms.
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PMID:Homocystinuria: studies on cystathionine beta-synthase, S-adenosylmethionine synthetase and cystathionase activities in skin fibroblasts. 678 21


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