Structure and mechanism of O-acetylserine sulfhydrylase

Wael Rabeh, Paul F. Cook

Research output: Contribution to journalShort survey

Abstract

The O-acetylserine sulfhydrylase (OASS) from Salmonella typhimurium catalyzes a β-replacement reaction in which the β-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 α-aminoacrylate intermediate. The enzyme is a homodimer with one pyridoxal 5′-phosphate (PLP) bound per subunit deep within the protein in a cleft between the N- and C-terminal domains of each of the monomers. All of the active site residues are contributed by a single subunit. The enzyme cycles through open and closed conformations as it catalyzes its reaction with structural changes largely limited to a subdomain of the N-terminal domain. The elimination of acetic acid from OAS is thought to proceed via an anti-E2 mechanism, and the only catalytic group identified to date is lysine 41, which originally participates in Schiff base linkage to PLP. The transition state for the elimination of acetic acid is thought to be asynchronous and earlier for Cβ-O bond cleavage than for Cα-H bond cleavage.

Original languageEnglish (US)
Pages (from-to)26803-26806
Number of pages4
JournalJournal of Biological Chemistry
Volume279
Issue number26
DOIs
StatePublished - Jun 25 2004

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Cysteine Synthase
Pyridoxal Phosphate
Acetic Acid
Serine
Salmonella
Schiff Bases
Enzymes
Salmonella typhimurium
Lysine
Cysteine
Conformations
Catalytic Domain
Acetates
Monomers
Kinetics
Proteins

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Structure and mechanism of O-acetylserine sulfhydrylase. / Rabeh, Wael; Cook, Paul F.

In: Journal of Biological Chemistry, Vol. 279, No. 26, 25.06.2004, p. 26803-26806.

Research output: Contribution to journalShort survey

Rabeh, Wael ; Cook, Paul F. / Structure and mechanism of O-acetylserine sulfhydrylase. In: Journal of Biological Chemistry. 2004 ; Vol. 279, No. 26. pp. 26803-26806.
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AB - The O-acetylserine sulfhydrylase (OASS) from Salmonella typhimurium catalyzes a β-replacement reaction in which the β-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 α-aminoacrylate intermediate. The enzyme is a homodimer with one pyridoxal 5′-phosphate (PLP) bound per subunit deep within the protein in a cleft between the N- and C-terminal domains of each of the monomers. All of the active site residues are contributed by a single subunit. The enzyme cycles through open and closed conformations as it catalyzes its reaction with structural changes largely limited to a subdomain of the N-terminal domain. The elimination of acetic acid from OAS is thought to proceed via an anti-E2 mechanism, and the only catalytic group identified to date is lysine 41, which originally participates in Schiff base linkage to PLP. The transition state for the elimination of acetic acid is thought to be asynchronous and earlier for Cβ-O bond cleavage than for Cα-H bond cleavage.

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