pcd Mutants of Streptomyces clavuligerus Still Produce Cephamycin C

Abstract

Biosynthesis of cephamycin C in Streptomyces clavuligerus involves the initial conversion of lysine to ␣-aminoadipic acid. Lysine-6-aminotransferase and piperideine-6-carboxylate dehydrogenase carry out this two-step reaction, and genes encoding each of these enzymes are found within the cephamycin C gene cluster. However, while mutation of the lat gene causes complete loss of cephamycin production, pcd mutants still produce cephamycin at 30% to 70% of wild-type levels. Cephamycin production by pcd mutants could be restored to wild-type levels either by supplementation of the growth medium with ␣-aminoadipic acid or by complementation of the mutation with an intact copy of the pcd gene. Neither heterologous PCR nor Southern analyses showed any evidence for the presence of a second pcd gene. Furthermore, cell extracts from pcd mutants lack detectable PCD activity. Cephamycin production in the absence of detectable PCD activity suggests that S. clavuligerus must have some alternate means of producing the aminoadipyl-cysteinyl-valine needed for cephamycin biosynthesis.

Evaluation of different media for the production of cephalosporins by Streptomyces clavuligerus ATCC 27064

“…The best results in terms of cephalosporin production were obtained using starch as the main source of C and energy. It is consistent with various studies which have suggested that the continuous and gradual hydrolysis of starch can avoid mechanisms of repression and /or inhibition in the production of β-lactam antibiotics that are normally triggered by C sources that are more easily metabolized by the microorganism, such as glucose or glycerol (Alexander et al 2007;Sánchez et al 2010). It has been observed that these easily assimilated sources can lead to an accumulation of intracellular phosphorylated compounds that drastically inhibit the expandase activity, which is the enzyme responsible for the expansion of the penicillin N ring of the β-lactam antibiotics biosynthetic pathway (Martín 2004;Zhu et al 2007).…”

Mutations in γ-aminobutyric acid (GABA) transaminase genes in plants or Pseudomonas syringae reduce bacterial virulence

“…gabT3 , in contrast, is not linked with any other genes predicted to be involved in GABA metabolism, and instead is adjacent to piperideine‐6‐carboxylate dehydrogenase ( pcD ). Protein association queries using the EMBL STRING database show that pcD is frequently located adjacent to, or in close proximity to transaminases similar to GabT, and piperideine‐6‐carboxylate dehydrogenase has been shown to act in conjunction with lysine‐6‐aminotransferase to convert lysine to α‐aminoadipic acid, an intermediate in lysine biosynthesis and catabolism and a precursor for antibiotic synthesis (Alexander et al. , 2007), which suggests that the primary activity of GabT3 may not be GABA transamination.…”

Genome-wide analysis of lysine catabolism in bacteria reveals new connections with osmotic stress resistance

“…Other actinomycetes that contain the LAT pathway produce pipecolate to serve as a substrate for antibiotic synthesis. In Streptomyces, for example, the LAT enzyme is considered to be the first step in the b-lactamic biosynthetic pathway (such as in cephamycin production) (Alexander et al, 2007). There is no evidence that the LAT pathway is involved in abiotic stress responses in these organisms.…”