NITRIC OXIDE-INDEPENDENT, THIOL-ASSOCIATED ADP-RIBOSYLATION INACTIVATES ALDEHYDE DEHYDROGENASE

Nitric oxide inhibits the activity of glyceraldehyde-3-phosphate dehyd rogenase and stimulates NAD-dependent automodification of a cysteine ( Dimmeler, S., Lottspeich, F., and Brune, B. (1992) J. Biol. Chem. 267, 16771-16774). Another NAD-utilizing dehydrogenase that has a catalyti c cysteine, aldehyde dehydrogenase (ALDH), was also inhibited by nitri c oxide. Unlike glyceraldehyde-3-phosphate dehydrogenase, ALDH was mod ified in a nitric oxide-independent process by ADP-ribose, but not by NAD. Modification, which proceeded to >2 mol ADP-ribose.mol ALDH-1, wa s associated with an exponential decrease in enzyme activity to less t han 10% of control. Two types of evidence suggested modification of th e ALDH-active site: 1) ADP-ribose inhibited ALDH competitively (K(i) = 0.46 mM) with respect to NAD (K(m) = 0.11 mm) in brief incubations an d 2) the presence of substrates protected ALDH from both modification and inhibition by ADP-ribose. The ALDH-ADP-ribose bond was sensitive t o base and mercuric ion and stable to acid and neutral hydroxylamine, properties shared with the ADP-ribosylcysteine linkage synthesized enz ymatically by pertussis toxin. These data demonstrate a novel means of inactivation of an NAD-dependent enzyme, namely the affinity-based mo dification of the enzyme NAD site by ADP-ribose, and suggest that none nzymatic ADP-ribosylation may be responsible for modification of cyste ine residues.