PMID:10993149
| Citation |
Mino, K, Yamanoue, T, Sakiyama, T, Eisaki, N, Matsuyama, A and Nakanishi, K (2000) Effects of bienzyme complex formation of cysteine synthetase from escherichia coli on some properties and kinetics. Biosci. Biotechnol. Biochem. 64:1628-40 |
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| Abstract |
Some properties and kinetics of the free and bound serine acetyltransferases (SATs) and O-acetylserine sulfhydrylase-As (OASS-As) from Escherichia coli were investigated. In some cases, SATdeltaC20, deleting 20 amino acid residues from the C-terminus of the wild-type SAT (Biosci. Biotechnol. Biochem., 63, 168-179 (1999)) was tested for comparison. The optimum pH and stability against some reagents for the free and bound wild-type SATs were similar except for the resistance to cold inactivation. The kinetics for the wild-type SAT and SATdeltaC20 followed a Ping-Pong Bi Bi mechanism with a mixed-type inhibition by L-cysteine. The kinetics and kinetic constants for the wild-type SAT were not changed by the complex formation with OASS-A. The optimum pH for OASS-A was shifted towards an alkaline pH by the complex formation. Thermal stability and stability against some reagents for the free and bound OASS-As were almost the same. On the other hand, the maximum velocity for OASS-A was lowered and dissociation constants for the substrates and products were increased by forming the complex with the wild-type SAT, although the kinetics for the free and bound enzymes followed the same Ping-Pong Bi Bi mechanism. From comparisons of computed courses of L-cysteine formation from L-serine using SAT (wild-type SAT and SATdeltaC20) and OASS-A with the experimental results and changes in the stability of the wild-type SAT by the complex formation, we discuss the role and significance of a complex formation for the cysteine synthetase. |
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| Keywords |
Acetyltransferases/metabolism; Cysteine/biosynthesis; Cysteine Synthase/metabolism; Dithionitrobenzoic Acid/metabolism; Escherichia coli/enzymology; Hydrogen-Ion Concentration; Kinetics; Protein Conformation; Serine/analogs & derivatives; Serine/metabolism; Serine O-Acetyltransferase |
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