Enzymatic conversion of the unnatural tripeptide .DELTA.-(D-.ALPHA.-aminoadipyl)-L-cysteinyl-D-valine to .BETA.-lactam antibiotics.

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Abstract
Incubation of the unnatural tripeptide .delta.-(D-.alpha.-aminoadipyl)-L-cysteinyl-D-valine (DLD-ACV) with a partially purified extract of Cephalosporium acremonium resulted in the production of deacetoxycephalosporin C. The extract contained isopenicillin N synthetase (cyclase) and deacetoxycephalosporin C synthetase (expandase) but no penicillin epimerase activity, and was incubated aerobically in the presence of the components of the cyclase and expandase reaction mixtures (Fe2+, ascorbate, dithiothreitol, .alpha.-ketoglutarate and ATP). The reaction was sensitive to penicillinase, indicating penicillin N to be an intermediate. When ring expansion was prevented by omission of .alpha.-ketoglutarate and ATP, no penicillin N was detected.