Characterisation of the citrate synthase reaction with propionyl-CoA.
Experiments with propionyl-CoA stereoselectively deuteriated in the propionyl moiety demonstrate that the formation of (2S,3S)-methylcitric acid (1) catalysed by citrate (si)-synthase occurs with inversion of configuration in the propionyl moiety; the absolute configurations of the methylcitric acids 1 and 2 indicate a si attack on oxaloacetate. Deuterium in the pro-S position is exchanged for protium 60 times faster than deuterium in the pro-R position. Experiments with (R,S)-(2-2H1)propionyl-CoA allowed the determination of isotope effects. For the enzymatic formation of 1, a primary deuterium isotope effect kH/kD = 1.8 and a secondary alpha-deuterium isotope effect kH/kD = 0.99 were calculated; both are effects on Vmax/KM.
D000214:Acyl Coenzyme A / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D002950:Citrate (si)-Synthase / Q000378:metabolism*; D003903:Deuterium; D007553:Isotope Labeling; D007700:Kinetics; D007652:Oxo-Acid-Lyases / Q000378:metabolism*; D013237:Stereoisomerism
D000214:Acyl Coenzyme A; C009061:propionyl-coenzyme A; D003903:Deuterium; D002950:Citrate (si)-Synthase; D007652:Oxo-Acid-Lyases