pcd Mutants of Streptomyces clavuligerus Still Produce Cephamycin C

Department of Biological Sciences, University of Alberta, Edmonton, Canada T6G 2E9

^* To whom correspondence should be addressed. Email: susan.jensen{at}ualberta.ca.

	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 30-70% 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 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.