2Tianjin University of Commerce, Tianjin 300134, P. R. China; fax: (86) 222-666-9775; E-mail: email@example.com
3College of Life Science, NanKai University, Tianjin 300071, P. R. China; fax: (86) 222-350-8371; E-mail: firstname.lastname@example.org
* To whom correspondence should be addressed.
Received July 15, 2008; Revision received August 27, 2008
A kinetic model describing the biosynthesis of L-cysteine by Pseudomonas sp. TS1138 has been developed. The two enzymes catalyzing this pathway, L-cysteine synthetase (CS) and L-cysteine desulfhydrase (CD), follow Michaelis–Menten kinetics with noncompetitive inhibition of CS by L-cysteine. From measurements of intermediates and end products that were made during L-cysteine enzymatic synthesis, metabolic control analysis of the pathway was carried out using the kinetic model. The elasticity coefficients and the flux control coefficients were calculated, and the analysis revealed a shift in the flux control from CS to CD during the reaction. The findings further implicate potential targets and strategies for increasing L-cysteine production; for example, the strain TS1138 could be manipulated by site-directed mutagenesis to reduce CD activity.
KEY WORDS: Pseudomonas sp. TS1138, L-cysteine, kinetic model, metabolic control analysis, enzymatic synthesis