Oxidation of Methanol by the Yeast,<i>Pichia pastoris</i>, Purification and Properties of the Formaldehyde Dehydrogenase

Abstract

The formaldehyde dehydrogenase (EC 1.2.1.1) from the yeast Pichia pastoris IFP 206 was purified to homogeneity. The enzyme had a molecular weight of 84,000 daltons and was composed of two identical subunits of a molecular weight of 39,000 daltons. The N-terminal end of the subunits is blocked. The protein showed 6,3 free -SH groups per mole and 12,5 in the presence of NAD+. Enzyme stability was increased by addition of glycerol during the purification. The enzyme activity is NAD+ and glutathione dependent. The reaction product is S formylglutathione. The presence of an S-formylglutathione hydrolase (EC 3.1.2.12) in the cell free extract was detected. The formaldehyde dehydrogenase showed an optimum pH of 7.9 and an optimum temperature of 47°C. The activation energy was 3.2 kcal/mol. The Michaelis constants for NAD+ and S-hydroxymethyl glutathione were respectively 0.24 mM and 0.26 mM.