Kinetics of human alcohol dehydrogenase with ring-oxidized retinoids: effect of Tween 80.
Human alcohol dehydrogenases (ADH1 and ADH4) actively use retinoids oxidized at the cyclohexenyl ring (4-oxo-, 4-hydroxy-, and 3,4-didehydro-retinoids), which are functional compounds in several cells and tissues (i.e., in human skin). Remarkably, activities with 4-oxo-retinal and 4-hydroxy-retinol (kcat = 2050 min(-1) for ADH4) are the highest among retinoids, similar to those of the best aliphatic alcohols. Thus, ADH1 and ADH4 provide a metabolic pathway for the synthesis of the corresponding retinoic acids. Tween 80, a widely used detergent in the retinoid activity assay, behaves as a competitive inhibitor. The Km values for all-trans-retinol (2-3 microM), estimated in the absence of detergent, are 10-fold lower than those obtained at the usual 0.02% Tween 80. This suggests a contribution of ADH to retinoid metabolism more relevant than previously expected. However, Tween 80 stabilizes retinoids in water solution and provides a reliable and reproducible assay, suitable for comparing different ADHs and different retinoid substrates.
Martras
Sílvia
S
Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
Alvarez
Rosana
R
Gallego
Oriol
O
Domínguez
Marta
M
de Lera
Angel R
AR
Farrés
Jaume
J
Parés
Xavier
X
D000426:Alcohol Dehydrogenase / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011136:Polysorbates / Q000494:pharmacology*; D015203:Reproducibility of Results; D012176:Retinoids / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D011136:Polysorbates; D012176:Retinoids; D000426:Alcohol Dehydrogenase