Effects of enhanced lysine epsilon-aminotransferase activity on cephamycin biosynthesis in Streptomyces clavuligerus.
A recombinant strain of S. clavuligerus (LHM100) that contains an additional copy of the gene (lat) encoding lysine epsilon-aminotransferase (LAT) was analyzed and compared to the wild-type for intracellular concentrations of primary metabolites involved in cephamycin C biosynthesis. This strain had been shown previously to produce higher levels of the antibiotic because of increased levels of LAT, a rate-limiting enzyme involved in the production of alpha-aminoadipic acid. The results showed that the overall growth kinetics of the two strains were comparable, including the intracellular concentrations of cysteine, valine and lysine. In contrast, 60% higher antibiotic production was observed in LHM100, which reflected a significant temporal variation in specific metabolite production rate. The time profile of LAT activity was consistently higher in LHM100; however, alpha-aminoadipic acid levels showed unexpected variation during the growth cycle. These results support the proposal that rate-limiting enzymes in cephamycin C biosynthesis are temporally controlled, and indicate that optimization of metabolite production will require differential overexpression of several biosynthetic genes.
Malmberg
L H
LH
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis 55455, USA.
Hu
W S
WS
Sherman
D H
DH
D002513:Cephamycins / Q000096:biosynthesis*; D051306:L-Lysine 6-Transaminase; D009842:Oligopeptides / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D013302:Streptomyces / Q000378:metabolism*; D000637:Transaminases / Q000502:physiology*
D002513:Cephamycins; D009842:Oligopeptides; C011638:5-(2-aminoadipyl)cysteinylvaline; D010088:Oxidoreductases; C038370:isopenicillin N synthetase; D000637:Transaminases; D051306:L-Lysine 6-Transaminase