Lysine catabolism and α-aminoadipate synthesis in Streptomyces clavuligerus

Abstract

The intracellular a-aminoadipic acid pool in Streptomyces clavuligerus mycelium growing in a starchpeptone medium decreased during the late exponential and stationary phases when cephamycin was being produced; however, the amino acid accumulated extracellularly. Although the specific activity of lysine e-aminotransferase (LAT) decreased during this period, there was no indication that the extracellular a-aminoadipic acid functioned as a precursor reserve for synthesis of the fl-lactam antibiotic. MeaSurement of LAT activity in cultures grown in defined media with starch and various nitrogen sources indicated that the enzyme was synthesized preferentially only during early growth. In its insensitivity to induction by a precursor, and in its susceptibility to carbon catabolite repression, LAT behaved as a secondary metabolic pathway enzyme. Unexpectedly, however, the enzyme increased in specific activity when cultures were supplemented with excess phosphate. Unlike LAT, cadaverine aminotransferase was inducible by Iysine or cadaverine and insensitive to phosphate; its features were consistent with a role in the catabolism of lysine by S. clavulioerus.

Localization of the lysine epsilon-aminotransferase (lat) and delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase (pcbAB) genes from Streptomyces clavuligerus and production of lysine epsilon-aminotransferase activity in Escherichia coli

“…LAT activity, and its gene, are specific to P-lactamproducing actinomycetes (20)(21)(22), and LAT now represents the first enzyme directed toward cephamycin C synthesis. Like ACVS and IPNS, two other early enzymes in the biosynthetic pathway, LAT in N. lactamdurans (15) and S.…”

“…clavuligerus (20,21) peaks in activity before exponential growth ends (prior to cephamycin production) and then declines. Other activities, epimerase and expandase, are subsequently produced and sustained during antibiotic production.…”

“…They were resuspended in 0.2 M potassium phosphate buffer (pH 7.5) and disrupted with ultrasound (six 10-s pulses with 1-min cooling intervals). The supernatant fluid from centrifugation (20 min, 10,000 x g, 4°C) was assayed for LAT activity by measuring the formation of 1-piperideine-6-carboxylate with an o-aminobenzaldehyde reagent as described previously (20).…”

Investigation of the biosynthesis of the pipecolate moiety of neuroprotective polyketide meridamycin

“…The e-deamination of L-lysine to form P6C can be catalyzed by a lysine-6-aminotransferase (for example, in the b-lactam antibiotic producing actinomycetes Streptomyces clavuligerus 19 and Nocardia lactamdurans, 20 or gram-negative bacteria Flavobacterium lutescence 21 ) or by an L-lysine-6-dehydrogenase as in Agrobacterium tumefaciens. 22 The enzyme dedicated to the second step in this pathway, the reduction of P6C to form pipecolate, has not been identified in bacteria.…”

Lysine is catabolized to 2-aminoadipic acid in Penicillium chrysogenum by an omega-aminotransferase and to saccharopine by a lysine 2-ketoglutarate reductase. Characterization of the omega-aminotransferase

“…In b-lactam-producing bacteria L-lysine is directly converted into 2-aminoadipic acid for cephamycin biosynthesis (Madduri et al 1991;Coque et al 1991). In these cases, the amino group on carbon 6 of the lysine molecule is transaminated to 2-ketoglutarate or another 2-ketoacid as the amino group acceptor, and the resulting 2-aminoadipic semialdehyde is subsequently oxidized to 2-aminoadipic acid (Pe´rez-Llarena et al 1998).…”