D-Glyceraldehyde 3-phosphate dehydrogenase; a comparison with liver aldehyde dehydrogenase

Using d-glyceraldehyde 3-phosphate, d-glyceraldehyde, and acetaldehyde as substrates, crude and crystalline preparations of d-glyceraldehyde 3-phosphate dehydrogenase from rabbit muscle have been investigated with respect to requirement for phosphate and arsenate (in acetaldehyde oxidation), pH optimum, rates of reactions, Michaelis constants, and inhibition by tetraethylthiuram disulfide (antabuse). Our crude preparation of d-glyceraldehyde 3-phosphate dehydrogenase has a much higher affinity for low concentrations of acetaldehyde than does the crystalline enzyme. Also, the rate of acetaldehyde oxidation as compared to glyceraldehyde oxidation is considerably higher with crude than with crystalline d-glyceraldehyde 3-phosphate dehydrogenase. However, most of our data suggest that d-glyceraldehyde 3-phosphate dehydrogenase may be the only DPN-linked aldehyde dehydrogenase in rabbit muscle.d-Glyceraldehyde 3-phosphate dehydrogenase, especially our crude preparation, has many properties in common with Racker's (10) preparation of liver aldehyde dehydrogeanse. However, Racker's (10) liver aldehyde dehydrogenase, which was somewhat purified, has not been shown to oxidize d-glyceraldehyde 3-phosphate. Investigations by various authors also indicate some other differences between aldehyde dehydrogenase from liver and d-glyceraldehyde 3-phosphate dehydrogenase from muscle. A further comparison of the two enzymes is warranted.d-Glyceraldehyde 3-phosphate dehydrogenase is strongly inhibited by tetraethylthiuram disulfide. The drug appears to compete with the substrate (d-glyceraldehyde 3-phosphate, d-glyceraldehyde, acetaldehyde) for the enzyme. The apparent dissociation constant for the enzyme-inhibitor complex is 5 × 10⁻⁶, M.