Pathway and Regulation of Lysine Biosynthesis inBrevibacterium lactofermentum

Abstract

The pathway and regulation of lysine biosynthesis in Brevibacterium lactofermentum were investigated. The biosynthetic pathway of l-lysine in Brevibacterium was the same as that in Escherichia coli, since biosynthetic enzymes, which were aspartokinase [EC 2.7.2.4], dihydrodipicolinate (DDP)* synthetase, DDP reductase and N-acetyl-ε-keto-α-aminopimelate (AKAP) synthetase, could be detected in B. lactofermentum. AKAP synthetase was measured with 1Δ-piperideine-2,6-dicarboxylate, which was prepared from l-diaminopimelate by l-amino acid oxidase, and either acetyl-CoA or succinyl-CoA could be served as an acyl donor for this reaction. Effect of amino acids on these enzymes was estimated. Aspartokinase was inhibited about 41, 45 and 82% by single or simultaneous addition of l-threonine and l-lysine at 1 mm, respectively, whereas the addition of other amino acids did not cause significant inhibitory effect. In contrast with DDP synthetase from E. coli, B. lactofermentum enzyme was not affected by l-lysine. DDP reductase was not inhibited by l-lysine, but about 56 and 47 % by l-cysteine and L-alanine at 10 mm, respectively. AKAP synthetase was not affected significantly by l-lysine at 10 mm. From the above results, the regulation mechanism of lysine biosynthesis in B. lactofermentum was discussed.