Mechanism of the Magnesium Ion Activation of the Catalytic Activity of Horse Liver Aldehyde Dehydrogenase
The activity of the pI 5 isozyme of horse liver aldehyde dehydrogenase is markedly enhanced by some divalent metal ions (Ca, Mn, Mg), inhibited by others (Fe, Cu, Cd), totally inhibited by Hg, and not significantly affected by still others (Zn, Ni, Co). Steady-state kinetics show that with 0.5 mM Mg or Mn a 2-fold activation of the velocity measured at pH 7.5 occurs when propionaldehyde is the substrate. In the pre-steady state, the magnitude burst of NADH formulation is increased from 2 moles formed per mole of tetrameric enzyme to 4 moles formed in the presence of Mg. The stoichiometry of coenzyme (NADH, NAD, ε-NAD) binding is also increased from essentially 2 moles binding to 4 moles binding per mole enzyme in the presence of Mg. It appears that the enzyme exhibits half of the site reactivity in the absence of metal but has a full complement of catalytic sites in the presence.
KeywordsAldehyde Dehydrogenase Scatchard Plot Tetrameric Enzyme Mole Enzyme Scientist Development Award
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- Feldman, R. I. and Weiner, H., 1972a, Horse liver aldehyde dehydrogenase. I. Purification and characterization, J. Biol. Chem., 247: 260.Google Scholar
- Feldman, R. I. and Weiner, H., 1972b, Horse liver aldehyde dehydrogenase. II. Kinetics and mechanistic implications of the dehydrogenase and esterase activity., J. Biol. Chem. 247: 267Google Scholar
- Venteicher, R., Mope, L., and Yonetani, T., 1977, Metal ion effectors of horse liver aldehyde dehydrogenase. In: “Alcohol and Aldehyde Metabolizing Systems,” Vol. II, R. G. Thurman et al., ed., Academic Press, New York.Google Scholar
- Weiner, H., Brown, C. S., Sanny, C. G., and Hu, J. H. J., 1976, Activation and inhibitors of horse liver aldehyde dehydrogenase, Fed. Proc., 35: 1499.Google Scholar
- Weiner, H., King, P., Hu, J. H. J., and Bensch, W. R., 1974, Mechanistic and enzymatic properties of liver aldehyde dehydrogenase. In: “Alcohol and Aldehyde Metabolizing Systems,” Vol. 1, R. G. Thurman et al., ed., Academic Press, New York.Google Scholar
- Weiner, H., Hu, J. H. J., and Sanny, C. G., 1976, Rate limiting steps for the esterase and dehydrogenase reaction catalyzed by horse liver aldehyde dehydrogenase, J. Biol. Chem., 251: 3857.Google Scholar