Functional analysis of L-serine O-acetyltransferase from Corynebacterium glutamicum

We report here the function of L-serine O-acetyltransferase (SAT) from the glutamic acid-producing bacterium Corynebacterium glutamicum. Based on the genome sequence of C. glutamicum and the NH(2)-terminal amino-acid sequence, the gene encoding SAT (cysE) was cloned and expressed in C. glutamicum. Deletion analysis of the 5'-noncoding region showed a putative -10 region ((-27)TTAAGT(-22) or (-26)TAAGTC(-21)) and a possible ribosome-binding site ((-12)AGA(-10)) just upstream from the start codon. We found that the SAT activity was sensitive to feedback inhibition by L-cysteine, and that SAT synthesis was repressed by L-methionine. Further, cysE-disrupted cells showed L-cysteine auxotrophy, indicating that C. glutamicum synthesizes L-cysteine from L-serine via O-acetyl-L-serine through the pathway involving SAT and O-acetyl-L-serine sulfhydrylase in the same manner as Escherichia coli.