Characterizing and engineering toluene o-xylene monooxygenase for the synthesis of common drug metabolites

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Project Summary/Abstract As drugs are metabolized in the body, their metabolites represent new chemical entities to which humans are exposed. Thus, investigating the toxicities and characterizing biological activities of drug metabolites is crucial for the development of safe, effective drugs. In fact, pharmacokinetic studies are critical components of investigational new drug applications to the US Food and Drug Administration. As a part of these studies, however, large quantities of pure metabolites are needed to characterize them in vitro and, especially in vivo. The chemical synthesis of drug metabolites is problematic in terms of yield, selectivity, and can be a major cost- driver in preclinical studies. Direct enzymatic synthesis of drug metabolites is an attractive alternative. Although P450 monooxygenase enzymes, found in human liver, have been in the spot light as drug metabolizing biocatalysts, many challenges still remain such as low biocatalytic activity, limited drug substrate specificity and product range. The investigation of alternate enzymes or biocatalysts may lead to a diversified metabolites product spectra and open up new horizons for efficient metabolite production. Due to its excellent chemistry, wide substrate range, and malleable catalytic activity, we propose to investigate the biocatalyst toluene o-xylene monooxygenase (ToMO) of Pseudomonas sp. OX1 as a drug metabolizing enzyme. Using protein engineering techniques, we plan to create ToMO variants with enhanced drug oxidation activity and fine-tuned specificity. Using protein engineering, we previously created several variants of ToMO for green chemistry and bioremediation applications. The prospect of using ToMO and its engineered variants for the synthesis of drug metabolites presents a new and exciting approach. Our long-term goal is to improve the versatility of ToMO even further by exploring and expanding its substrate repertoire for drug development and pharmaceutical production. The specific aims of this project are to characterize wild-type ToMO for drug oxidation activity with 6 different drug substrates and drug-like candidates including aniline, acetanilide, bupropion, ticlopidine, chlorphenamine, and omeprazole (Aim 1), construct ToMO variant libraries using protein engineering and screen for further improvements (Aim 2), and sequence, model, and characterize positive ToMO variants for drug oxidation activity (Aim 3).