Ethanol oxidation in the microsomal fraction of rat liver

Roach, Mary K.; Reese, W.N.; Creaven, Patrick J.

doi:10.1016/0006-291x(69)90346-5

Cited by 85 publications

(21 citation statements)

References 7 publications

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“…This is not surprising, however, since added H,O, is rapidly converted into H,O and 0, by the catalatic reaction of catalase. Later, it was demonstrated that a continuous supply of hydrogen peroxide, such as by added xanthine oxidase plus hypoxanthine or by glucose oxidase plus glucose, was capable of supporting high rates of acetaldehyde production from ethanol in liver microsomes [4,5]. This clearly indicated a role of catalase in microsomal ethanol oxidation.…”

Section: Is Microsomal Nadph-dependent Ethanol Oxidation Due To a Permentioning

confidence: 91%

“…Lieber and DeCarli [4] and Roach et al [5] reported a 40°/, inhibition with CO:O, ratios of 10, whereas Orme-Johnson and Ziegler [3] observed no inhibition with lower ratios. I n our studies, acetaldehyde production from ethanol in the presence of carbon monoxide was variable but tended toward inhibition a t high CO:O, ratios.…”

Section: Is Microsomal Nadph-dependent Ethanol Oxidation a Mixed Funcmentioning

confidence: 97%

“…I n the presence of both an NADPH-or an H202-generating system, azide inhibited the production of acetaldehyde from ethanol in microsomes [4,5] (Fig.4 and 6). Halfmaximal inhibition was observed with azide concentrations of less than 50 pM (Fig.6).…”

Section: Inhibition By Azidementioning

confidence: 99%

“…First, ethanol is a well known peroxidatic substrate for catalase [Z], provided that hydrogen peroxide is present. Second, the microsomal fraction of liver is capable of converting ethanol into acetaldehyde in the presence of NADPH and oxygen [3,4], a process which is partially inhibited by carbon monoxide [4,5]. This requirement for NADPH and oxygen and the sensitivity to carbon monoxide are characteristic for microsomal mixed-function oxidation systems.…”

mentioning

confidence: 99%

“…For example, aminotriazole, an inhibitor of the biosynthesis of catalase [ 121, diminished the production of acetaldehyde from ethanol in the presence of an NADPH-generating system and led to the suggestion that ethanol oxidation is due to a coupled reaction involving NADPH oxidase and catalase [5,11].…”

mentioning

confidence: 99%

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Hepatic Microsomal Ethanol Oxidation

Thurman

Ley²,

Scholz³

1972

European Journal of Biochemistry

578

192

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Microsomes from rat liver form hydrogen peroxide in the presence of an NADPH-generating system in proportion to protein concentrations as determined by three independent methods : ferrithiocyanate, cytochrome c peroxidase, and scopoletin fluorescence. Maximal rates observed were about 15 pmol H,O,/g microsomal protein per minute. The oxygen concentration for half-maximal rates was 50 pM. It is suggested that NADPH-dependent hydrogen peroxide formation in microsomes is mainly due to NADPH oxidase; however, partial inhibition by carbon monoxide suggests that about one third arises from the autoxidation of cytochrome P-450.Similarities exist between microsomal acetaldehyde production from ethanol (i.e. the microsomal ethanol-oxidizing system of Lieber and DeCarli [4]) and hydrogen peroxide formation : viz. requirement for NADPH and oxygen, identical oxygen concentrations for halfmaximal rates, and sensitivity to carbon monoxide. Microsomal acetaldehyde production in the presence of either an NADPH-or an H,O,-generating system exhibits identical characteristics as follows: (a) ethanol concentration for half-maximal rates (i.e. 12 mM); (b) dependency of maximal rates on rates of hydrogen peroxide formation; (c) competitive inhibition by peroxidatic substrates for catalase, e.g. formate (half-maximal effect: 150 mM); (d) inhibition by catalase inhibitors, e.g. azide (half-maximal effect : 50 pM), with identical azide insensitive rates ; (e) diminished acetaldehyde production in microsomes from rats pretreated with aminotriazole or pyrazole with identical residual rates. Moreover, NADPH-dependent acetaldehyde production is suppressed in the presence of an active H,O,-utilizing system. Thus, it is concluded that the NADPH-dependent microsomal ethanol-oxidizing system of Lieber and DeCarli [4] is due to a hydrogen peroxide formation from NADPH and a subsequent peroxidation of ethanol by contaminating catalase. The data indicate that the existence of a unique system in addition to the peroxidatic reaction of catalase as postulated recently [4] is highly doubtful.

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Section: Is Microsomal Nadph-dependent Ethanol Oxidation Due To a Permentioning

confidence: 91%