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

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 Na₂HPO₄–0.02 M citric acid, pH 6.8, containing 0.33 mM MgSO₄, 0.1 mM thiamine pyrophosphate, 2.5 mM MnSO₄ 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 FeSO₄·7H₂O, MnSO₄, thiamine pyrophosphate, β-mercaptoethanol, MgSO₄, CaCO₃, and NaCl, and inhibited by AgNO₃, HgCl₂, CuSO₄, ZnSO₄, SnCl₂, NH₄Cl, (CH₃COO)₂Pb·3H₂O, iodoacetic acid, FeCl₃·6H₂O, and (NH₄)₂SO₄. Its molecular weight was 96,000 by sedimentation equilibrium, and 100,000 by Sephadex G-200 column chromatography.