Further studies of the action of disulfiram and 2,2'-dithiodipyridine on the dehydrogenase and esterase activities of sheep liver cytoplasmic aldehyde dehydrogenase.
1. Pre-modification of cytoplasmic aldehyde dehydrogenase by disulfiram results in the same extent of inactivation when the enzyme is subsequently assayed as a dehydrogenase or as an esterase. 2. 4-Nitrophenyl acetate protects the enzyme against inactivation by disulfiram, particularly well in the absence of NAD+. Some protection is also provided by chloral hydrate and indol-3-ylacetaldehyde (in the absence of NAD+). 3. When disulfiram is prevented from reacting at its usual site by the presence of 4-nitrophenyl acetate, it reacts elsewhere on the enzyme molecule without causing inactivation. 4. Enzyme in the presence of aldehyde and NAD+ is not at all protected against disulfiram. It is proposed that, under these circumstances, disulfiram reacts with the enzyme-NADH complex formed in the enzyme-catalysed reaction. 5. Modification by disulfiram results in a decrease in the amplitude of the burst of NADH formation during the dehydrogenase reaction, as well as a decrease in the steady-state rate. 6. 2,2'-Dithiodipyridine reacts with the enzyme both in the absence and presence of NAD+. Under the former circumstances the activity of the enzyme is little affected, but when the reaction is conducted in the presence of NAD+ the enzyme is activated by approximately 2-fold and is then relatively insensitive to the inactivatory effect of disulfiram. 7. Enzyme activated by 2,2'-dithiodipyridine loses most of its activity when stored over a period of a few days at 4 degrees C, or within 30 min when treated with sodium diethyldithiocarbamate. 8. Points for and against the proposal that the disulfiram-sensitive groups are catalytically essential are discussed.
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives / Q000494:pharmacology*; D000444:Aldehyde Dehydrogenase; D000445:Aldehyde Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D003593:Cytoplasm / Q000201:enzymology; D004220:Disulfides; D004221:Disulfiram / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004950:Esterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D012756:Sheep
D004220:Disulfides; D011725:Pyridines; D009243:NAD; C001105:2,2'-dipyridyl disulfide; D015082:2,2'-Dipyridyl; D000445:Aldehyde Oxidoreductases; D000444:Aldehyde Dehydrogenase; D004950:Esterases; D004221:Disulfiram