J. Cornforth, G. T. Phillips, B. Messner
Mar 1, 1974
Citations
1
Influential Citations
20
Citations
Journal
European journal of biochemistry
Abstract
1 Synthetic specimens of R-[2H1, 3H1]acetate and of S-[2H1, 3H1]acetate were converted into coenzyme A thiolesters. 2 Each of these thiolesters was condensed with acetoacetyl-CoA on 3-hydroxy-3-methyl-glutaryl-CoA synthase. 3 The products, which were found to be hydroxymethylglutaryl-phosphopantetheines owing to a secondary cleavage of the coenzyme A moieties, were reduced chemically to 3R mevalonates. 4 Each mevalonate specimen, after mixing with [2-14C]mevalonate, was converted into squalene and cholesterol by a rat liver preparation. 5 Each cholesterol specimen was converted into androst-1,4-diene-3,17-dione by incubation with a strain of Mycobacterium phlei in the presence of an inhibitor. 6 When the procedures 4 and 5 were carried out with authentic specimens of 2R- and 2S-[2-3H1]mevalonate, it was found that the androstadienedione had lost nearly all tritium derived from the 2S-mevalonate but had retained nearly all tritium (relative to 14C) derived from the 2R-mevalonate. 7 The androstadienedione derived, by procedures 1–5, from R-acetate showed a loss of more than half of its tritium (relative to 14C). The androstadienedione derived by the same procedure from S-acetate lost less than half of its tritium. 8 It is concluded that the reaction on hydroxymethylglutaryl-CoA synthase is stereospecific and is associated with an intramolecular hydrogen isotope effect. If this effect is normal (kH/kD>1) then the condensation proceeds with inversion of configuration at the methyl group.