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)

Rabbit antiserum raised against pure human hepatic cystathionine beta-synthase was used to precipitate synthase from extracts of radiolabeled cultured fibroblasts derived from 17 homocystinuric patients and two controls. Size analysis of the immunoprecipitates by SDS/polyacrylamide gel electrophoresis revealed that 15 of the 17 synthase-deficient lines synthesized synthase subunits indistinguishable in size from the control (Mr = 63,000). One mutant fibroblast line, previously shown to lack catalytic activity and antigenically cross-reacting material, contained no immunoprecipitable product. Analyses of immunoprecipitated polypeptides synthesized in vitro by cell-free translation of mRNAs prepared from selected mutants confirmed and extended the results from cell extracts. This experimental approach also allowed us to determine the biochemical and genetic defect in a patient with barely detectable synthase subunits in cell extracts. His cultured fibroblasts and those of his father contained two mRNA species, separable by size, coding for equal amounts of two immunoprecipitable polypeptides: one of normal size (Mr = 63,000); the other approximately 7,000 daltons smaller (Mr = 56,000). His mother's fibroblasts made only the Mr = 63,000 species. We conclude that this patient is a compound heterozygote, and that one of his mutant alleles results in the synthesis of a synthase polypeptide missing about 60 amino acid residues.
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PMID:Homocystinuria: biogenesis of cystathionine beta-synthase subunits in cultured fibroblasts and in an in vitro translation system programmed with fibroblast messenger RNA. 671 64

Polyclonal antibodies against cysteine synthase (CSase; EC 4.2.99.8) isozymes 1, 2, and 3 were used for the detection of complexes of these isozymes with serine acetyltransferase (SATase; EC 2.3.1.30). SATase was partially purified and found to complex with these isozymes by western blotting and immunotitration. When the complexes were treated with a high concentration of O-acetyl-L-serine, they did not dissociate. However, some complexes with CSase 1 or 3 dissociated when left for 24 h at 4 degrees C. Results of western blotting on SDS-PAGE showed that CSase 2 complexed with SATase. CSases 1, 2, and 3 all could complex with SATase, but the tightness of the bond differed.
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PMID:Complexes of serine acetyltransferase and isozymes of cysteine synthase in spinach leaves. 964 25

Misfolding of mutant enzymes may play an important role in the pathogenesis of cystathionine beta-synthase (CBS) deficiency. We examined properties of a series of 27 mutant variants, which together represent 70% of known alleles observed in patients with homocystinuria due to CBS deficiency. The median amount of SDS-soluble mutant CBS polypeptides in the pellet after centrifugation of bacterial extracts was increased by 50% compared to the wild type. Moreover, mutants formed on average only 12% of tetramers and their median activity reached only 3% of the wild-type enzyme. In contrast to the wild-type CBS about half of mutants were not activated by S-adenosylmethionine. Expression at 18 degrees C substantially increased the activity of five mutants in parallel with increasing the amounts of tetramers. We further analyzed the role of solvent accessibility of mutants as a determinant of their folding and activity. Buried mutations formed on average less tetramers and exhibited 23 times lower activity than the solvent exposed mutations. In summary, our results show that topology of mutations predicts in part the behavior of mutant CBS, and that misfolding may be an important and frequent pathogenic mechanism in CBS deficiency.
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PMID:Cystathionine beta-synthase mutations: effect of mutation topology on folding and activity. 2050 25