A three-dimensional homology model of the O-acetylserine sulfhydrylase-B from Salmonella typhimurium |
| |
Authors: | Rabeh Wael M Mather Timothy Cook Paul F |
| |
Institution: | Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, Oklahoma 73019, USA. |
| |
Abstract: | O-acetylserine sulfhydrylase (OASS) catalyzes the last step in the cysteine biosynthetic pathway in enteric bacteria and plants. The overall pathway involves the substitution of the beta-acetoxy group of O-acetyl-L-serine with inorganic bisulfide. Two isozymes are present in S. typhimurium, the A- and B-isozymes, expressed under aerobic and anaerobic conditions, respectively. No crystal structure is presently available for the B-isozyme. Kinetic data indicate the catalytic mechanism of OASS-B is ping-pong, as found for the A-isozyme, but kinetic parameters and substrate specificity differ. In order to estimate whether structural differences may be responsible for the kinetic differences, a homology model was built using the structure of OASS-A as the template for the OASS-B model. The beta-subunit of tryptophan synthase and cystathionine beta-synthase were used for comparison. Differences between the OASS-A structure and the homology model for OASS-B are discussed. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|