Abstract: Glycerol-3-phosphate dehydrogenase (EC1.1.1.8)has been isolated from the unicellular green algae Dunaliella salina (Dunal) Teed. and the electrophoretic homogenous enzyme was obtained by PEG fractionation and column chromatography on DEAE Sepharose Fast Flow, Blue Sepharose CL 6B and Mono Q HRS/5. The purified enzyme has a specific activity of 12.6 U/mg and a molecular weight of about 270 kD determined by native gradient polyacrylamide gel electrophoresis (4% to 20% acrylamide). The enzyme has only one kind of 65 kD subunit determined by SDS-PAGE. Combining the results from the two kinds of electrophoresis, the authors deduce that the enzyme may be a tetramer. The optimum pH is 7.5 for reduction of dihydroxyacetone phosphate (DHAP) and 10 for glycerol-3-phosphate (G-3-P) oxidation. The apparent Km for reduced nicotinamide adenine dinucleotide (NADH), DHAP, nicotinamide adenine dinucleotide (NAD), G-3-P are 63 μmol/L, 272 μmol/L, 1.53 mmol/L, 6.52 mmol/L, respectively. The enzyme is unstable during storage. NADH can delay activity losing, but NAD can not. NaC1 at low concentration protects the enzyme, whereas at high concentration NaC1 accelerates the activity loss of the stored enzyme. The higher the concentration, the faster the activity loss.

Key words: Dunaliella salina, Osmoregulation, Glycerol-3-phosphate dehydrogenase, Purification, Kinetic Property