EFFECTS OF ENHANCED LYSINE EPSILON-AMINOTRANSFERASE ACTIVITY ON CEPHAMYCIN BIOSYNTHESIS IN STREPTOMYCES-CLAVULIGERUS

A recombinant strain of S. clavuligerus (LHM100) that contains an addi tional copy of the gene (lar) encoding lysine epsilon-aminotransferase (LAT) was analyzed and compared to the wild-type for intracellular co ncentrations of primary metabolites involved in cephamycin C biosynthe sis. This strain had been shown previously to produce higher levels of the antibiotic because of increased levels of LAT, a rate-limiting en zyme involved in the production of alpha-amino-adipic acid. The result s showed that the overall growth kinetics of the two strains were comp arable, including the intracellular concentrations of cysteine, valine and lysine. In contrast, 60% higher antibiotic production was observe d in LHM100, which reflected a significant temporal variation in speci fic metabolite production rate. The time profile of LAT activity was c onsistently higher in LHM100, however, alpha-aminoadipic acid levels s howed unexpected variation during the growth cycle. These results supp ort the proposal that rate-limiting enzymes in cephamycin C biosynthes is are temporally controlled, and indicate that optimization of metabo lite production will require differential overexpression of several bi osynthetic genes.