Synthesis, characterization, and enzymic conversion of nonhydrolysable analogues of propionylcoenzyme A

Article abstract of DOI:10.1139/v94-025

We describe the synthesis of three novel analogues of propionyl-coenzyme A, in which the sulfur atom has been replaced by methylene, ethylene, and thiomethylene, respectively. All three analogues, propionyl-dethia(carba)-CoA (1), propionyl-dethia-(dicarba)-CoA (2), and S-(2-oxobutanyl)-CoA (3)were characterized by ¹H and ³¹ P NMR spectroscopy and FAB mass spectrometry. Propionyl-CoA-oxaloacetate transcarboxylase from Propionibacterium shermanii accepted the novel analogues as substrates and carboxylated them to the corresponding methylmalonyl-CoA analogues (4-6). The latter were further converted into the succinyl-CoA analogues by the coenzyme-B₁₂-dependent methylmalonyl-CoA mutase from the same organism. The succinyl-CoA analogues, succinyl-dethia(carba)-CoA (7), succinyl-dethia(dicarba)-CoA (8), and 4-carboxy(2-oxobutanyl)CoA (9) were obtained on a preparative scale and their Michaelis constants (K(m)) with methylmalonyl-CoA mutase were determined to be 0.136, 2.20, and 0.132 mM, respectively (K(m) for succinyl-CoA is 0.025 mM). The V(max) values for 7, 8, and 9 are 1.1, 0.013, and 0.0047 μmol min^-1 U^-1, respectively (V(max) for succinyl CoA is 1.0). The utility of the novel coenzyme A analogues in enzyme mechanistic studies is discussed.