Latent inhibitors. Part 2. Allylic inhibitors of alcohol dehydrogenase

Abstract

The syntheses of a number of 3-substituted prop-2-en-l -ols and -1 -als, required for studying the latent inhibition of horse liver alcohol dehydrogenase (E.C. 1.1.1 .I ), are described. Substituents were chosen to cover a range of alkoxide, phenolate, thiolate, and halide leaving groups. Of the compounds studied, only 3-ethylthioprop-2-en-l-01 proved to be a latent inhibitor through oxidation to the corresponding aldehyde, catalysed by the enzyme. The persistence of inhibition caused by this inhibitor is shown, by product studies and kinetic measurements, to be due to ethanethiol, formed by an enzyme-catalysed hydrolysis of the aldehyde. TABLE 1 Inhibition properties of the compounds studied a Krn IM Kl I M Inhibition propcrties Competitive, b slow inactivation 1.54 x 10-4 1.25 x lea 6.4 x 10-4 5.0 x los6 1 . 3 x 10-6 5.2 x 1 0 -4 Perkin I Competitive; no time-dependent inactiva-Neither substrate nor inhibitor No time-dependent inactivation tion, forms malonic dialdehyde No time-dependent inactivation Competitive, no time-dependent inactiva-Rapid covalent inhibition at 1 0 -s ~, 4 = 2 tion, forms malonic dialdehyde min Rapid covalent inhibition at 1 0 -6 ~, ti = 30s No time-dependent inactivation Competitive, reversible No time-dcycndciit inactivation 6.2 x lo-' Competitive, reversible Compounds were assayed at pH 9 in the presence of NAL) (1.5 x l P 3 ~) , using 3.76 x l0-'-1.5 x 1 W 6 ~ lIL.4DH. Q ' Conipetitive refers to competition with ethanol.[0/1182 Received, 28th JuZy, 108OJ

Active-site directed inactivation of rat ovarian 20 α-hydroxysteroid dehydrogenase

“…It was felt that the C-20 a-allylic alcohol could be oxidized by the dehydrogenase to the corresponding vinyl ketone, which could then act as a Michael acceptor and inactivate the enzyme. In this manner the allylic alcohols would act as suicide substrates in a fashion similar to that described by Maclnnes et al (1981) for alcohol dehydrogenase. Evaluation of the racemic mixture of C-20 epimeric alcohols indicated that they cannot be utilized as substrates even when highly favourable conditions for oxidation were employed (i.e.…”

“…In considering candidates that might promote irreversible inhibition of the ovarian 20a-hydroxysteroid dehydrogenase we were attracted to the previous studies of Maclnnes on alcohol dehydrogenase (Maclnnes et al, 1981). These studies showed that alcohol dehydrogenase catalyses the oxidation of allylic alcohols to yield the corresponding Michael acceptors (a,fl-unsaturated aldehydes), which, when generated within the proximity ofthe active site, can undergo alkylation to produce inactivated enzyme.…”

In Situ Manganese Dioxide Alcohol Oxidation−Wittig Reactions: Preparation of Bifunctional Dienyl Building Blocks

“…Thus, ethyl propiolate 5a was readily converted into the Z-bromoacrylate 6, 8a and propriolic acid 5b into E-bromoacylate 7, 8b using published stereoselective procedures (Scheme 2). Reduction with lithium aluminum hydride 9 then gave the requisite 3-bromopropenols 3Z and 3E in good overall yield as pure stereoisomers. These compounds were then subjected to the in situ alcohol oxidation-Wittig conditions using (carboethoxymethylene)triphenylphosphorane.…”

Studies of enzyme inhibition by compounds containing small rings

“…Our interest in the enzyme chemistry of compounds containing small rings developed from a speculative study of the inhibition of alcohol dehydrogenase by allylic alcohols (MacInnes et al, 1981) in which we found that 3-thioethylprop-2-en-1-01 (I) was a potent inhibitor of this enzyme. Our original strategy was that oxidation of (I) would lead to an a,/?-unsaturated aldehyde to which a nucleophile at the active site would add leading to the inhibited enzyme.…”