Alpha,beta-elimination reaction of O-acetylserine sulfhydrylase. Is the pyridine ring required?
O-Acetylserine sulfhydrylase (OASS) catalyzes the elimination of acetate from O-acetyl-L-serine (OAS) followed by addition of bisulfide to give L-cysteine. Site-directed mutagenesis has been used to replace the active site serine, S272, which forms a hydrogen bond to N1 of pyridoxal 5'-phosphate (PLP) with alanine and aspartate. Based on UV-visible spectral and steady-state kinetic studies, both mutant enzymes catalyze the elimination reaction with an efficiency equal to that of the wild-type enzyme. Data are consistent with an anti-E(2) reaction proposed for the elimination reaction.
Cook
Paul F
PF
Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, OK 73019, USA. pcook@chemdept.chem.ou.edu
D003547:Cysteine Synthase / Q000737:chemistry*; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D011725:Pyridines / Q000737:chemistry*; D013329:Structure-Activity Relationship
D011725:Pyridines; D003547:Cysteine Synthase; C023666:pyridine