Enzymatic in vitro reduction of ketones. Part 2. Study of coenzyme recycling in an ethanol–cyclohexanone system with HLAD (Horse Liver Alcohol Dehydrogenase)

Abstract

The coupled-substrate recycling system is elaborated for a reaction mixture containing cyclohexanone–ethanol (as coupled substrate), the co-enzyme NAD⁺, and the enzyme HLAD. All reaction parameters are discussed in order to optimize the reduction of cyclohexanone as a model compound for other reductions, mainly to synthesize chiral compounds. With catalytic amounts of co-enzyme 50 000 recyclings could be realized. A formula for the initial rate of the enzymatic reaction based on a double Theorell–Chance mechanism is given and experimentally checked.