Purification and properties of a new enzyme, propioin synthase in baker's yeast which forms propioin from propionaldehyde

Abstract

The new enzyme, propioin synthase, concerned with the formation of propioin from propionaldehyde was purified 270-fold from the crude enzyme in a yield of 28% by protamine sulfate precipitation, ammonium sulfate fractionation and G-200 gel chromatography using citrate-phosphate buffer (0.1 M Na 2HPO 4–0.02 M citric acid, pH 6.8, containing 0.33 mM MgSO 4, 0.1 mM thiamine pyrophosphate, 2.5 mM MnSO 4 and 30 mM β-mercaptoethanol). The purified enzyme was homogeneous on disc gel electrophoresis. It was most active at pH 6.8–7.0 and 37°C, and stable at pH 7–8 and below 45°C. Its activity was enhanced by FeSO 4·7H 2O, MnSO 4, thiamine pyrophosphate, β-mercaptoethanol, MgSO 4, CaCO 3, and NaCl, and inhibited by AgNO 3, HgCl 2, CuSO 4, ZnSO 4, SnCl 2, NH 4Cl, (CH 3COO) 2Pb·3H 2O, iodoacetic acid, FeCl 3·6H 2O, and (NH 4) 2SO 4. Its molecular weight was 96,000 by sedimentation equilibrium, and 100,000 by Sephadex G-200 column chromatography.