Candida parapsilosis carbonyl reductase as a tool for preliminary screening of inhibitors for alcohol dehydrogenase induced skin sensitization

Abstract

Human alcohol dehydrogenases, specifically ADH1 oxidize primary alcohols to aldehydes in the skin. These aldehydes act as haptens, leading to sensitization. Inhibition of these ADH enzymes may help in combating skin allergies. In the present study, the recombinantly purified stereospecific enzyme from Candida parapsilosis ATCC 7330, Candida parapsilosis Carbonyl Reductase (CpCR) has 23.31 % sequence similarity with human alcohol dehydrogenase ADH1B1. These two enzymes have perfectly overlapping cofactor and zinc binding domains. CpCR was found to oxidize primary alcohols to their corresponding aldehydes. Oxidation of primary alcohols by CpCR was further optimized with cinnamyl alcohol as the model substrate that initially showed a conversion of 56 % ± 0.25, and upon optimization increased to 98.2 % ± 0.23. An increase of 20–50 % in the conversion rate has been observed for various primary alcohols under the optimized reaction conditions. A simple and efficient model was designed for the screening of compounds that inhibit CpCR with the possibility of mitigating the action of skin allergens by inhibiting ADH1. p-Nitrophenylglyoxal (PNG) was found to be a good inhibitor for CpCR which showed inhibitory activity at very low concentration (IC50,100 mM ± 1.27) as compared to the standard inhibitor 4-methyl pyrazole (4MP) (IC50, 400 mM ± 2.05).