Overall mechanism and rate equation for O-acetylserine sulfhydrylase.
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منابع مشابه
Structure and mechanism of O-acetylserine sulfhydrylase.
The O-acetylserine sulfhydrylase (OASS) from Salmonella typhimurium catalyzes a beta-replacement reaction in which the beta-acetoxy group of O-acetyl-L-serine (OAS) is replaced by bisulfide to give L-cysteine and acetate. The kinetic mechanism of OASS is ping-pong with a stable alpha-aminoacrylate intermediate. The enzyme is a homodimer with one pyridoxal 5'-phosphate (PLP) bound per subunit de...
متن کاملFormation of -cyanoalanine by O-acetylserine sulfhydrylase.
Cell-free extracts of Bacillus megaterium form beta-cyanoalanine (beta-CNA)-(14)C from Na(14)CN and l-cysteine, O-acetyl-l-serine or, to a lesser extent, l-serine. However, the presence of cyanide in the growth medium does not increase the capacity of cell extracts to catalyze the formation of beta-CNA from cysteine and cyanide. The formation of beta-CNA is readily detected in extracts of cells...
متن کاملO-Acetylserine sulfhydrylase from Methanosarcina thermophila.
Cysteine is the major source of fixed sulfur for the synthesis of sulfur-containing compounds in organisms of the Bacteria and Eucarya domains. Though pathways for cysteine biosynthesis have been established for both of these domains, it is unknown how the Archaea fix sulfur or synthesize cysteine. None of the four archaeal genomes sequenced to date contain open reading frames with identities t...
متن کاملSurface-exposed tryptophan residues are essential for O-acetylserine sulfhydrylase structure, function, and stability.
O-Acetylserine sulfhydrylase is a homodimeric enzyme catalyzing the last step of cysteine biosynthesis via a Bi Bi ping-pong mechanism. The subunit is composed of two domains, each containing one tryptophan residue, Trp50 in the N-terminal domain and Trp161 in the C-terminal domain. Only Trp161 is highly conserved in eucaryotes and bacteria. The coenzyme pyridoxal 5'-phosphate is bound in a cle...
متن کاملThe structural gene for O-acetylserine sulfhydrylase A in Salmonella typhimurium. Identity with the trzA locus.
Mutants of Salmonella typhimurium, resistant to 1,2,4triazole and mapping in the trzA and trzB loci, have been found to have low to virtually absent levels of 0-acetylserine sulfhydrylase activity while remaining prototrophic for cysteine. Kinetic, chemical, and immunochemical studies of the highly purified enzymes from two trzA mutants prove that both strains bear mutant alleles for 0-acetylse...
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ژورنال
عنوان ژورنال: Journal of Biological Chemistry
سال: 1977
ISSN: 0021-9258
DOI: 10.1016/s0021-9258(17)40412-1