ABSTRACT
G-1-P dehydrogenase from M thermoautotrophicum Ml has a molecular mass of approximately 302 kDa and consists of a single subunit of 38 kDa. The enzyme appears to be a homooctamer. The purified enzyme was active for both DHAP and G-1-P. NADPH as well as NADH was active as a hydrogen donor. No activity was observed for G-3-P, oglyceraldehyde, glycerol, or dihydroxyacetone. Kinetic constants were determined in the both directions of DHAP reduction and G-1-P oxidation. K,. for DHAP (2.17 mmolll) was 7.5 times smaller than that for G-1-P (16.3 mmol/l), indicating that the formation of G-1-P is the natural direction catalysed by the enzyme in the cell. The presence of a.-GP (a racemic mixture ofG-1-P and G-3-P) in the assay mixture did not inhibit the enzyme activity up to 500 mmol/l, indicating that neither G-1-P nor G-3-P inhibits G-1-P synthesis.
