Substrate stereochemistry of the enoyl-CoA hydratase reaction.
1. A specimen of stereospecifically 2-tritiated 3-hydroxybutyric acid was prepared by hydroboration of ethyl crotonate. It was assumed that the hydroboration reaction took a syn course and hence that (2R,3S) plus (2S,3R)-3-hydroxy[2 minus 3H1]butyric acid was formed after oxidation and hydrolysis. 2. 3RS-3-Hydroxy[2 minus 3H2]butyric acid, symmetrically tritiated at C-2, was prepared by isotopic exchange of ethyl acetoacetate in tritiated water, followed by reduction and hydrolysis. 3. The 3R-enantiomers of the acids listed under paragraphs (1) and (2) were destroyed enzymically by use of 3R-specific 3-hydroxybutyrate dehydrogenase and the residual 3S-enantiomers were isolated. 4. The resulting specimens of 2R,3S-3-hydroxy[2 minus 3H1]butyric acid and 3S-3hydroxy[2 minus 3H2]-butyric acid were converted chemically to the acyl-CoA derivatives. These were incubated with enoyl-CoA hydratase. 5. In the presence of the enoyl-CoA hydratase symmetrically labelled 3S-3-hydroxy[2 minus 3H2]BUTYRYL-CoA lost nearly 50% of its tritium label; 2R,3S-3hydroxy [2-3-H1]butyryl-CoA lost about 78%. 6. It was concluded that the elimination of the elements of water from 3-hydroxybutyryl-CoA on the hydratase occurs stereospecifically with syn geometry.
D000090:Acetoacetates; D000818:Animals; D001894:Borohydrides; D001896:Boron Compounds; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D003065:Coenzyme A; D003437:Crotonates; D006836:Hydro-Lyases; D006884:Hydroxybutyrate Dehydrogenase; D006885:Hydroxybutyrates / Q000138:chemical synthesis; D007553:Isotope Labeling; D008930:Mitochondria, Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D014316:Tritium
D000090:Acetoacetates; D001894:Borohydrides; D001896:Boron Compounds; D003437:Crotonates; D006885:Hydroxybutyrates; D014316:Tritium; D006884:Hydroxybutyrate Dehydrogenase; D006836:Hydro-Lyases; D003065:Coenzyme A