Purification, characterization and NNK carbonyl reductase activities of 11beta-hydroxysteroid dehydrogenase type 1 from human liver: enzyme cooperativity and significance in the detoxification of a tobacco-derived carcinogen.
11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD 1) physiologically catalyzes the interconversion of receptor-active 11-hydroxy glucocorticoids (cortisol) to their receptor-inactive 11-oxo metabolites (cortisone), thereby acting as important pre-receptor control device in regulating access of glucocorticoid hormones to the glucocorticoid receptor. Evidence is emerging that 11beta-HSD 1 fulfills an additional role in the detoxification of non-steroidal carbonyl compounds, by catalyzing their reduction to the corresponding hydroxy derivatives that are easier to conjugate and eliminate. Whereas a number of methods were ineffective in purifying 11beta-HSD 1 from human liver, this membrane-bound enzyme was successfully obtained in an active state by a purification procedure that took advantage of a gentle solubilization method as well as providing a favourable detergent surrounding during the various chromatographic steps. We could demonstrate that 11beta-HSD 1 is active as a dimeric enzyme which exhibits cooperativity with cortisone and dehydrocorticosterone (11-oxoreducing activity) as substrates. Accordingly, this enzyme dynamically adapts to low (nanomolar) as well as to high (micromolar) substrate concentrations, thereby providing the fine tuning required as a consequence of great variations in circadian plasma glucocorticoid levels. Due to this kinetic peculiarity, 11beta-HSD 1 is also able to even metabolize nanomolar concentrations of the tobacco-specific nitrosamine 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK), a fact which is important in view of the relatively low levels of this carcinogen observed in smokers. Finally, 11beta-HSD 1 is potently (in nM concentrations) inhibited by glycyrrhetinic acid, the main constituent of licorice. Licorice, however, in addition to being a confectionary, serves as a major cigarette additive, which is used in cigarette manufacturing as a taste and flavour intensifier. Hence, licorice exposure may affect NNK detoxification by inhibition of 11beta-HSD 1, a condition which may advance lung cancer incidence, especially in smokers expressing low levels of this enzyme. Collectively, our data expand insights into the multifunctional nature of hydroxysteroid dehydrogenases/carbonyl reductases and emphasize the importance of 11beta-HSD 1 in the detoxification of a tobacco-derived carcinogen, in addition to its endocrinological functions.
Maser
Edmund
E
Department of Experimental Toxicology, Faculty of Medicine, University of Kiel, Brunswiker Strasse 10, D-24105, Kiel, Germany. maser@toxi.uni-kiel.de
Friebertshäuser
Jutta
J
Völker
Bernhard
B
D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D042842:11-beta-Hydroxysteroid Dehydrogenases; D001483:Base Sequence; D002273:Carcinogens / Q000493:pharmacokinetics*; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008658:Inactivation, Metabolic; D008099:Liver / Q000201:enzymology*; D009602:Nitrosamines / Q000493:pharmacokinetics*; D010802:Phylogeny; D014026:Nicotiana / Q000737:chemistry*
D002273:Carcinogens; D017931:DNA Primers; D009602:Nitrosamines; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; D006913:Hydroxysteroid Dehydrogenases; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D042842:11-beta-Hydroxysteroid Dehydrogenases; C468386:HSD11B1 protein, human