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However, in crude extracts containing ATP and coenzyme A, penicillin acylase may be confused with a mixture of MMSA:CoA ligase (Section ΙΙΙ,Β) and acylCoA : 6-APA acyltransferase (Section ΙΙΙ,Ε). It should be possible to isolate penicillin acylase from P. chrysogenum (identified by catalysis of phenoxyacetic acid + 6-APA —» penicillin V + H 2 0) for comparison to the highly purified preparations of acylCoA : 6-APA acyltransferase (identified by its ability to catalyze phenoxyacetylCoA + 6-APA —> penicillin V + CoA and inability to catalyze phenoxyacetic acid + 6-APA —> penicillin V + H 2 0).

QUEENER AND NORBERT NEUSS of a mixture of NADH, dithiotreitol, and DL-6-methyl-5,6,7,8-tetrahydropterin to reaction mixtures containing enzyme, ascorbate, ferrous sulfate, and α-ketoglutarate resulted in lower yields of cephalosporins than those obtained in reaction mixtures to which the addition was not made (Hook et al, 1979). Yoshida et al. (1978) measured the ability of extracts of cephalosporin C-negative mutants for the ability to convert 18a to 22. Mutants of type A, represented by M-0198, M-0199, and M-2351, produced no ß-lactam antibiotics in vivo and their extracts converted 18a to 22.

Clavuligerus that lack the dioxygenase that converts 22 to 23 have not been reported. Cell-free conversion studies (see discussion in VI,C) suggest that such mutants would accumulate 22 but would not efficiently produce 7a-methoxycephalosporins. VI. Synthesis of Cephalosporins and 7a-Methoxycephalosporins A. Conversion of Deacetylcephalosporin C to Cephalosporin C Deacetylcephalosporin C (23) is the immediate biosynthetic precursor of cephalosporin C (24) in C. acremonium. , 1976). Buffered extracts of the parents or of revenants of these mutants can convert 23 to 24 in the presence of acetylCoA and Mg2+ (Fujisawa and Kanzaki, 1975b).