Retinol dehydrogenase from bovine retinal rod outer segments. Kinetic mechanism of the solubilized enzyme.

Retinol dehydrogenase solubilized by Lubrol 12A9 from bovine retinal rod outer segments forms mixed micelles of Stokes radius 8.5 nm. The kinetic properties of the solubilized retinol dehydrogenase were examined and retinaldehyde reduction and retinol oxidation were seen to proceed at pH 8.3 by a sequential Ordered Bi Bi mechanism. This conclusion was supported by bisubstrate initial velocity studies, dead-end and product inhibition. The kinetic mechanism of retinol dehydrogenase is not altered by the effect of Lubrol until a concentration of 2 mM is reached, at which the detergent lowers the values of the Michaelis and dissociation constants. The catalytic rate of the retinol dehydrogenase is significantly lowered by detergent in the range of pH 3 to 9.