@article{2bbbd9c1d8974eb0acbc6d26eadebaf9,
title = "Characterization of human erythrocyte aldehyde dehydrogenase",
abstract = "Human erythrocyte aldehyde dehydrogenase was purified to homogeneity. The enzyme exhibited a single band of activity on starch gel electrophoresis and on isoelectric focusing. It was a tetramer with an estimated molecular weight of 230,000 daltons and an isoelectric point of 5.0. Its pH optimum of 8.5, Michaelis-Menten constant for acetaldehyde of 46 μM, and high sensitivity to noncompetitive inhibition by disulfiram resembled human liver cytosolic aldehyde dehydrogenase. Low concentrations of magnesium (5-10μM) resulted in enhancement of erythrocyte aldehyde dehydrogenase activity, whereas higher physiological concentrations of magnesium resulted in uncompetitive inhibition of enzyme activity. Magnesium inhibited the enzyme activity by increasing the binding of NADH to the enzyme as had been found to be the case for the inhibitory effect of magnesium on the human liver cytosolic enzyme. Erythrocyte aldehyde dehydrogenase may metabolize small amounts of acetaldehyde escaping the liver during ethanol metabolism and protect extrahepatic tissues from acetaldehyde toxicity.",
author = "Rawles, {James W.} and Rhodes, {Deborah L.} and Potter, {James J.} and Esteban Mezey",
note = "Funding Information: for NAD+ is in the range previously reported for physiologicl evels of magnesium.A bove thesel evels the liver cytosolic enzyme [8]a nd for the purified the enzyme activity was uncompetitivelyi nhibited erythrocyte enzyme [3]T.h e mitochondrial enzyme by magnesiumw ith respectt o both substratea nd is reported to have a higher K,,f,or NAD+ [20]. coenzyme.T wo-dimensionalk inetic analysisd emon-The physiologicalf unction of erythrocytea ldehyde strated increased enzyme affinity for aldehyde, dehydrogenaseis not known. A significant role in NAD+, and NADH in the presenceo f inhibitory aldehydem etabolismi s suggestedb y a number of levels of magnesium.I n addition, magnesiumw as observations.O rientals with disulfiram-likef lushing also shown to increase binding of NAD+ to the attacksin responset o alcoholi ngestionh avee levated enzyme binding sites by fluorescenceq uenching. blood levels of acetaldehydea nd moderately de-With the exception of the slight activation at very pressede rythrocytea ldehyded ehydrogenasaec tivity low magnesiumle vels, qualitativelyi dentical effects [22]. Chronic alcoholics have similarly lowered on overall rate and kinetic constantsw ere demon-activity of erythrocytea ldehyded ehydrogenasea nd stratedf or the human liver cytosolic enzyme[ 6]. It elevatedc irculatinga cetaldehydein responset o alco-has been shown that NADH dissociationi s the rate-hol ingestion [4,23]. However, Orientals with alco-determinings tep for the liver cytosolice nzymea nd hol-induced flushing have been shown to lack the that the increasedb inding affinity for NADH caused liver mitochondrial aldehyde dehydrogenase[ 24], by magnesiumr esultsi n decreasede nzymec atalytic and chronic alcoholisma lsor educest he hepaticc yto-rate. The behavioro f the human liver mitochondrial solic enzyme activity [5]. Hence, it is difficult to enzymei s different in that magnesiuma ctivatest he ascertain the importance of erythrocytea ldehyde catalytic rate probably by increasing hydrolysis of dehydrogenasein overall acetaldehydem etabolism. the enzyme*product.NADH.Mgz+in termediate[ 6]. It is acceptedt hat most acetaldehydem etabolism The findings of an inhibitory effecto f magnesiumo n occurs in the liver [25]. The observation of a erythrocytea ldehyde dehydrogenasein dicate that substantialg radientb etweenh epaticv ein (2-20 PM) decreases in the enzyme activity observed in and peripheralv enous (< 2 PM) acetaldehydele vels alcoholics[ 4] are not explainedb y changesin eryth-suggestst hat extrahepaticm etabolism occurs [2]. rocyte magnesiumc oncentrationw hich is decreased This could be mediatedb y aldehyded ehydrogenase after chronic ethanol consumption[ 7]. found in blood and many other tissues[ l] and may Disulfiram stronglyi nhibited erythrocytea ldehyde serve to protect theset issuesf rom the toxic effects dehydrogenasein a noncompetitive manner. The of the small amounts of acetaldehydee scapingt he inhibition was reversedb y 2-mercaptoethanowl hich liver or generatedb y non-hepatice thanol oxidation also activated the control enzyme, probably by [25].T he observeds ubstratea ffinitiesa re not incon-regeneratingc atalyticallyi mportant free sulfhydryl sistentw ith this hypothesis.T he estimatedp otential groupsw hich are oxidizedb y disulfirama s well as by aldehydeo xidizing capacityo f the blood in a 70 kg intrinsic oxidants.T hese observationsc onfirm those man approximates6 .8 pmol/min basedo n an enzyme of Inoui et al. [3] and are similar to those with the activityo f 1.31n mol/ml blood/min [18],a nd a blood liver cytosolic aldehyded ehydrogenase[8 ]. volume of 75 ml/kg of body weight. However, the significanceo f erythrocytea ldehyded ehydrogenase Acknowledgements-This work was supported by Grant activity must be interpretedi n the light of the intra-AA 00 626 from the United StatesP ublic Health Service erythrocytem ilieu. Foundation. and by the Alcoholic Beverage Medical Research Magnesiumi s the major intracellular divalentc at- ion and, as such, may have a significanti nfluenceo n aldehyded ehydrogenasaec tivityi n vivo. The current study showeda slight activationo f erythrocytea lde- hyde dehydrogenaseb y very low (< 10, uM), non-",
year = "1987",
month = nov,
day = "1",
doi = "10.1016/0006-2952(87)90025-6",
language = "English (US)",
volume = "36",
pages = "3715--3722",
journal = "Biochemical Pharmacology",
issn = "0006-2952",
publisher = "Elsevier Inc.",
number = "21",
}