NADPHQuinone Reductases NQOs EC 1655

Subcellular location: Cytosol.

Organ distribution: Liver, brain, and gut. High expression in tumors. These enzymes are also targets for activation of prodrugs.

Cofactors: NADH and NADPH for NQO1; N-ribosyl-dihydroni-cotinamide (NRH) for NQO2.

Reaction: Reduction of quinones, nitroarenes, N-oxides, and hydroxylamines.

Inhibitors: Dicoumarol and warfarin.

Table 2.11. Summary of enzymes involved in the oxidation and/or reduction of alcohols, aldehydes, ketones, and carboxylic acids

Enzyme (cofactor, cellular

Substrate

Metabolite

location)

Alcohol (primary)

Aldehyde

ADH (NAD+, cytosol)

Alcohol (secondary)

Ketone

ADH (NAD+, cytosol) AKR (NAD(P)+, cytosol)

Alcohol (tertiary)

No reaction

Aldehyde

Alcohol (primary)

ADH (NAD+, cytosol) ALR (NAD(P)+, cytosol) AKR (NAD(P)+, cytosol) ALDH (NAD(P)+, cytosol, ER, mitochondria)

Ketone

Alcohol (secondary)

AKR (NAD(P)+, cytosol) Carbonyl reductase (NADPH, cytosol, ER) Aldehyde reductase (NAD (P)+, cytosol)

Aldehyde

Carboxylic acid

ALDH

Carboxylic acid

No reduction

ADH Alcohol dehydrogenase; AKR aldo-keto reductase; ALDH aldehyde dehydrogenase; ER endoplasmic reticulum; NAD nicotinamide adenine dinucleotide; NADPH nicotinamide adenine dinucleotide phosphate

Was this article helpful?

0 0

Post a comment