Inhibition of ALDH3A1-catalyzed oxidation by chlorpropamide analogues (vol130, pg 135, 2001)

In our efforts to identify agents that would specifically inhibit ALDH3A1, we had previously studied extensively the effect of an N-1-alkyl, an N-1-me thoxy, and several N-1-hydroxy-substituted ester derivatives of chlorpropam ide on the catalytic activities of ALDH3A1s derived from human normal stoma ch mucosa (nALDH3A1) and human tumor cells (tALDH3A1), and of two recombina nt aldehyde dehydrogenases, viz. human rALDH1A1 and rALDH2. The N-1-methoxy analogue of chlorpropamide, viz. 4-chloro-N-methoxy-N-[(propyl amino)carbo nyl]benzenesulfonamide (API-2), was found to be a relatively selective and potent inhibitor of tALDH3A1-catalyzed oxidation as compared to its ability to inhibit nALDH3A-catalyzed oxidation, but even more potently inhibited A LDH2-catalyzed oxidation, whereas an ester analogue, viz. (acetyloxy)[(4-ch lorophenyl)sulfonyl]carbamic acid 1,1-dimethylethyl ester (NPI-2), selectiv ely inhibited tALDH3A1-catalyzed oxidation as compared to its ability to in hibit nALDH3A1-, ALDH1A1- and ALDH2-catalyzed oxidations, and this inhibiti on was apparently irreversible. Three additional chlorpropamide analogues, viz. 4-chloro-N,O-bis(ethoxycarbonyl )-N-hydroxybenzenesulfonamide (NPI-4), N,O-bis(carbomethoxy)methanesulfohydroxamic acid (NPI-5), and 2-[(ethoxyca rbonyl)oxy]-1,2-benzisothiazol-3(2H)-one 1,1-dioxide (NPI-6), were evaluate d in the present investigation. Quantified were NAD-linked oxidation of ben zaldehyde catalyzed by nALDH3A1 and tALDH3A1, and NAD-linked oxidation of a cetaldehyde catalyzed by rALDH1A1 and rALDH2, all at 37 degreesT and pH 8.1 , and in the presence and absence of inhibitor. NPI-4, NPI-5 and NPI-6 were not substrates for the oxidative reactions catalyzed by any of the ALDHs s tudied, Oxidative reactions catalyzed by the ALDH3A1s, rALDH1A1 and rALDH2 were each inhibited by NPI-4 and NPI-5. NPI-6 was a poor inhibitor of nALDH 3A1- and tALDH3A1-catalyzed oxidations, but was a relatively potent inhibit or of rALDH1A1- and rALDH2-catalyzed oxidations. In all cases, inhibition o f ALDH-catalyzed oxidation was directly related to the product of inhibitor concentration and preincubation (enzyme + inhibitor) time. As judged by th e product values ( muM x min) required to effect 50% inhibition (IC50): (1) nALDH3A1 and tALDH3A1 were essentially equisensitive to inhibition by NPI- 4 and NPI-5, and both enzymes were poorly inhibited by NPI-6; (2) rALDH1A1 was, relative to the ALDH3A1s, slightly more sensitive to inhibition by NPI -4 and NPI-5, and far more sensitive to inhibition by NPI-6, and (3) rALDH1 A1 was, relative to rALDH2, essentially equisensitive to inhibition by NPI- 5, whereas, it was slightly more sensitive to inhibition by NPI-4 and NPI-6 . (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.