Methyl glutaconyl-CoA

This biotin-dependent enzyme [EC 6.4.1.4] catalyzes the reaction of ATP with 3-methylcrotonyl-CoA and bicarbonate to produce ADP, orthophosphate, and 3-methyl-glutaconyl-CoA. 

This enzyme [EC 4.2.1.18] catalyzes the conversion of (5)-3-hydroxy-3-methylglutaryl-CoA to trans-3-methyl-glutaconyl-CoA and water. 

After dehydrogenation to 234, X = SCoA, the catabolism of leucine 205 (Scheme 62c) differs from that of the other branched-chain amino acids. A biotin-dependent carboxylation leads to the acid 236, X = SCoA, which is hydrated to HMG-CoA 237, a compound involved in isoprenoid biosynthesis. Feeding stereospecifically labeled samples of leucine in studies of terpenoid biosynthesis indicated that the ( )-methyl group was carboxylated without isomerization of the double bond (181, 182). Messner, Cornforth et al. (215) investigated the hydration 236 = 237 catalyzed by the enzyme 3-methyl-glutaconyl-CoA hydratase (EC 4. 2. 1. 18) and showed that the reversible reaction had syn stereospecificity. 

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