Related Experiment Video
Updated: Aug 19, 2026

LC-MS Analysis of Human Platelets as a Platform for Studying Mitochondrial Metabolism
Published on: April 4, 2016
Carbonyl reduction of metyrapone in human liver
1Department of Pharmacology and Toxicology, School of Medicine, University of Marburg, Lahn, Federal Republic of Germany.
Abstract:
Carbonyl reduction was investigated in cytosolic and microsomal fractions of human liver using the ketone metyrapone as a substrate. The cytosolic enzyme has a stronger preference for NADPH over NADH than the microsomal enzyme: the former shows only 14% of the NADPH-supported activity while the latter exhibits 36% activity with NADH. Barbitone and quercitrin, the classic inhibitors of carbonyl reductases, do not affect metyrapone reduction in either fraction. Dicumarol and indomethacin, the specific inhibitors of NAD(P)H: quinone-oxidoreductase and dihydrodiol dehydrogenase, respectively, only slightly decreased metyrapol formation. In contrast, 5 alpha-dihydrotestosterone, the active form of the androgen steroid testosterone, inhibited metyrapone reduction very strongly in the microsomal fractions and is postulated to be the physiological substrate of the enzyme. This resembles the situation in mouse liver [E. Maser and K. J. Netter, Biochem Pharmacol 38: 3049-3054, 1989] where microsomal metyrapone reductase was inhibited by steroids and the purified enzyme was demonstrated to mediate androsterone oxidation. Immunoblot analysis revealed antigenic cross-reaction of antibodies against the 34 kDa metyrapone reductase from mouse liver microsomes with the homologous protein in human liver microsomes pointing to structural homologies between the respective enzymes of the two species. These results--together with previous findings, which have shown that there exist functional as well as structural relationships between microsomal mouse liver metyrapone reductase and 3 alpha-hydroxysteroid dehydrogenase from Pseudomonas testosteroni [E. Maser, U. Oppermann and K. J. Netter, Eur J Pharmacol 183:1366, 1990]--suggest that metyrapone reduction in human liver microsomes might be catalysed by a microsomal hydroxysteroid dehydrogenase.
More Related Videos
Related Concept Videos
Alcohols from Carbonyl Compounds: Reduction
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
Preparation of Aldehydes and Ketones from Nitriles and Carboxylic Acids
Reducing carboxylic acid derivatives like acyl chlorides (RCOCl), esters (RCO2R′), and nitriles (RCN) using milder aluminum hydride agents like lithium tri-tert-butoxyaluminum hydride [LiAlH(O-t-Bu)3] and diisobutylaluminum hydride [DIBAL-H] allows...
Preparation of Aldehydes and Ketones from Carboxylic Acid Derivatives
Carboxylic acid derivatives like acid chlorides and esters are more easily reducible than the corresponding acids. The derivatives reduce in the presence of mild reducing agents to give aldehydes. Aldehydes can also be prepared by Rosenmund reduction, that is, the reduction of acid...
Drug Metabolism: Phase I Reactions
Phase I Reactions: Oxidation of Aliphatic and Aromatic Carbon-Containing Systems
Oxidation reactions are fundamental in aromatic carbon-containing systems. An example is the hydroxylation of phenobarbital, a process that transforms it into...
Phase I Reactions: Reductive Reactions

