Abstract
Abstract An enzymatic system which reduces nicotinamide N-oxide to nicotinamide was isolated from hog liver and purified about 280-fold. The reduction is dependent on the presence of reduced diphosphopyridine nucleotide or a low molecular weight constituent found in boiled liver supernatant. The two cofactors appear to be involved in the expression of two distinct enzymatic activities. Evidence has been presented which indicates both activities may be associated with a single protein or enzymatic unit. The DPNH-dependent reaction is the following. H+ + DPNH + nicotinamide N-oxide → DPN+ + nicotinamide + H2O The nature of the supernatant-dependent reaction is not completely understood, since the identity of the compound which is oxidized in the course of reduction of the N-oxide is not known.
Highlights
An enzymatic system which reduces nicotinamide N-oxide to nicotinamide was isolated from hog liver and purified about 280-fold
After intravenous administration of nicotinic acid N-oxide to rats, Tatsumi and Kanamitsu [6] detected nicotinic acid in the urine. They were able to demonstrate the reduction of nicotinic acid N-oxide in perfused rabbit liver, but were
While studying the role of nicotinamide in the squalene oxidocyclase system, Chaykin and Bloch [9] noted that nicotinamide N-oxide occasionally produced a marked stimulation of the oxidocyclase activity. They demonstrated that rats formed nicotinamide N-oxide in vivo, and that hog liver homogenates catalyzed its reduction to nicotinamide
Summary
An enzymatic system which reduces nicotinamide N-oxide to nicotinamide was isolated from hog liver and purified about 280-fold. After intravenous administration of nicotinic acid N-oxide to rats, Tatsumi and Kanamitsu [6] detected nicotinic acid in the urine They were able to demonstrate the reduction of nicotinic acid N-oxide in perfused rabbit liver, but were. While studying the role of nicotinamide in the squalene oxidocyclase system, Chaykin and Bloch [9] noted that nicotinamide N-oxide occasionally produced a marked stimulation of the oxidocyclase activity They demonstrated that rats formed nicotinamide N-oxide in vivo, and that hog liver homogenates catalyzed its reduction to nicotinamide. Precipitated nicotinamide N-oxide reduction that was dependenton boiled protein was removed by centrifugation for 10 min at 27,000 X g. The supernatant was heated in a boiling water bath for an addi- ml of 50% (w/v) trichloracetic acid, and the precipitated protein tional 10 min, centrifuged, and lyophilized. Unlessotherwisenoted, the standard incubation mixture (0.5 ml) contained 5.43 pmolesof nicotinamide N-oxide, 0.65
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