Abstract
Nitric oxide inhibits the activity of glyceraldehyde-3-phosphate dehydrogenase and stimulates NAD-dependent automodification of a cysteine (Dimmeler, S., Lottspeich, F., and Brüne, B. (1992) J. Biol. Chem. 267, 16771-16774). Another NAD-utilizing dehydrogenase that has a catalytic cysteine, aldehyde dehydrogenase (ALDH), was also inhibited by nitric oxide. Unlike glyceraldehyde-3-phosphate dehydrogenase, ALDH was modified in a nitric oxide-independent process by ADP-ribose, but not by NAD. Modification, which proceeded to > 2 mol ADP-ribose.mol ALDH-1, was associated with an exponential decrease in enzyme activity to less than 10% of control. Two types of evidence suggested modification of the ALDH-active site: 1) ADP-ribose inhibited ALDH competitively (Ki = 0.46 mM) with respect to NAD (Km = 0.11 mM) in brief incubations and 2) the presence of substrates protected ALDH from both modification and inhibition by ADP-ribose. The ALDH-ADP-ribose bond was sensitive to base and mercuric ion and stable to acid and neutral hydroxylamine, properties shared with the ADP-ribosylcysteine linkage synthesized enzymatically by pertussis toxin. These data demonstrate a novel means of inactivation of an NAD-dependent enzyme, namely the affinity-based modification of the enzyme NAD site by ADP-ribose, and suggest that nonenzymatic ADP-ribosylation may be responsible for modification of cysteine residues.
Published Version
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