Cephalosporin formation by cell-free extracts from Streptomyces clavuligerus.

Abstract
Cell-free extracts of S. clavuligerus convert .delta.-L-(.alpha.-aminoadipyl)-L-cysteinyl-D-valine (ACV) into an antibiotic product which is 30-50% penicillinase-insensitive. TLC resolves this antibiotic product into 1 major penicillinase-sensitive component and 1 major and 1 minor penicillinase-resistant component. The major and minor penicillinase-resistant antibiotics co-chromatograph with deacetoxycephalosporin C and deacetylcephalosporin C, respectively. Ring expansion of a penicillin intermediate, as evidenced by the production of penicillinase-resistant antibiotic, shows an absolute requirement for .alpha.-ketoglutarate, while ATP, K+ and Mg2+ have lesser effects. Ring expansion activity is not sedimented by high speed centrifugation and is unaffected by membrane-disrupting treatments. Penicillin N and ACV (presumably via penicillin N) are the only substrates so far accepted by the ring expanding enzyme. New syntheses of penicillin N and isopenicillin N are described.

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