- Cephalosporin biosynthesis: A branched pathway sensitive to an isotope effect
-
Incubation of penicillin N (3a) with partially purified deacetoxy/deacetylcephalosporin C synthase (DAOC/DAC synthase) from Cephalosporium acremonium CO 728 gave in addition to the expected products, deacetoxycephalosporin C and deacetylcephalosporin C, a third β-lactam metabolite as a 3β-hydroxy-3α-methylcepham (9a). Production of the 3β-hydroxycepham was promoted from [3-2H]penicillin N (3b) which was rationalised by the operation of a kinetic isotope effect on a branched pathway in the enzymic process. The oxygen of the 3β-hydroxy group was shown to be derived in part from molecular oxygen. In addition, the 2β-methyl group of penicillin N was shown to be incorporated into C2 of the 3β-hydroxy-3α-methylcepham, a result in stereochemical accord with the equivalent transformation of the 2β-methyl group of penicillin N into C2 of deacetoxycephalosporin C1. A mechanistic interpretation, consistent with these observations, is offered.
- Baldwin,Adlington,Crouch,Schofield,Turner,Aplin
-
p. 9881 - 9900
(2007/10/02)
-
- Cephalosporin C Biosynthesis; a Branched Pathway Sensitive to a Kinetic Isotope Effect
-
Incubation of penicillin N with preparations of deacetoxycephalosporin C/deacetylcephalosporin C synthetase activity from Cephalosporium acremonium CO 728 gave, along with the normal product deacetoxycephalosporin C, another β-lactam metabolite, namely 7β--3β-hydroxy-3α-methyl4-2H)-cepham-4α-carboxylic acid.This material arises as a result of a deuterium isotope effect on a branched pathway in the enzymic mechanism.The 3β-hydroxy group in this substance arises from molecular oxygen.
- Baldwin, Jack E.,Adlington, Robert M.,Aplin, Robin T.,Crouch, Nicholas P.,Knight, Graham,Schofield, Christopher J.
-
p. 1651 - 1654
(2007/10/02)
-