Inactivation of horse liver mitochondrial aldehyde dehydrogenase by disulfiram. Evidence that disulfiram is not an active-site-directed reagent

Abstract

The inhibition of mitochondrial (pI 5) horse liver aldehyde dehydrogenase by disulfiram (tetraethylthiuram disulphide) was investigated to determine if the drug was an active-site-directed inhibitor. Stoichiometry of inhibition was determined by using an analogue, [35S]tetramethylthiuram disulphide. A 50% loss of the dehydrogenase activity was observed when only one site per tetrameric enzyme was modified, and complete inactivation was not obtained even after seven sites per tetramer were modified. Modification of only two sites accounted for a loss of 75% of the initial catalytic activity. The number of functioning active sites per tetrameric enzyme, as determined by the magnitude of the pre-steady-state burst of NADH formation, did not decrease until approx. 75% of the catalytic activity was lost. These data indicate that disulfiram does not modify the essential nucleophilic amino acid at the active site of the enzyme. The data support an inactivation mechanism involving the formation of a mixed disulphide with a non-essential cysteine residue, resulting in a lowered specific activity of the enzyme.

Esterase activity of high-Km aldehyde dehydrogenase from rat liver mitochondria

“…Kitson (1978) observed that the dehydrogenase activity was more susceptible to disulfiram inhibition than the esterase activity of the sheep enzyme. Nevertheless, disulfiram, which modified the catalytically essential group of sheep liver cAldDH (Kitson 1987), did not react with the essential residue of horse liver mAldDH (Sanny and Weiner 1987). In the present study, both chloral hydrate and disulfiram acted as competitive inhibitors for the esterase and dehydrogenase activities of rat liver of mAldDH.…”

Thiram inhibits angiogenesis and slows the development of experimental tumours in mice

“…TR was previously shown to inhibit also other enzymes such as aldehyde dehydrogenase, aldehyde oxidase and rat lipoprotein lipase activity in adipose tissue (Freundt and Netz, 1977;Sanny and Weiner, 1987;Sadurska and Boguszewski, 1993). None of these enzymes is copper dependent.…”

Targeting of Nuclear Factor-κB and Proteasome by Dithiocarbamate Complexes with Metals

“…However, incorporation could be detected within the first few minutes when ALDH was inhibited by disulfiram [75]. It seems that the ALDH inhibition by disulfiram is caused by the formation of an intramolecular disulfide bond between the active site thiol and the thiol of another cysteine residue [76][77]. Nevertheless, there are other possible mechanisms of disulfiram inhibitory action on ALDH via its metabolites [78][79][80][81][82][83][84].…”