Screening for novel hydroxylations by P450 biocatalysis. (News Briefs).

Industries involved in manufacture of fine chemicals, pharmaceutical precursors such as the intermediates for Taxol or of high performance materials such as the polymers in bulletproof vests are searching for new synthesis routes to make relevant chemical building blocks. In many cases, these building block chemicals contain aromatic functionality or require specific patterns of oxygenation along a chemical backbone. Oxygenated benzocycloarenes (fused benzenecycloalkane structures) are a class of such useful reactants that are hard to make by traditional organic synthesis routes. Biocatalysis is a particularly attractive alternative for making these compounds and has the additional advantage of doing so by green, environmentally friendly syntheses.

A project at NIST is focused on development of enzymes, tools for screening enzymes, and measurements of enzyme-catalyzed reactions that can apply to these industrial needs. The work builds on one of the human liver's principal drug-metabolizing enzymes, cytochrome P450 monooxygenase. Earlier work in the project showed that these enzymes are useful as biocatalysts for hydroxylation of benzocycloarenes to regio- and stereospecific alcohols. Now experimental and theoretical studies with wild type enzyme and an engineered mutant have shown that hydroxylation is regiospecific at the 1-position for a family of benzocycloarene compounds: benzocyclobutene, benzocyclopentene (indian), benzocyclohexene (tetralin), and benzocycloheptene.

A major scientific conclusion was that reaction energetics predominated over active site steric constraints so that quantum mechanical calculations comparing the energetics of all possible radical intermediates successfully predicted the hydrocylation patterns for all products. An important technological aspect was the development of a rapid spectroscopic assay for identifying potential targets of P450 catalysis in a high-through-put screening format. The work has been published in the New Journal of Chemistry, Vol. 26, pp. 35-42 (2002).

CONTACT: Vince Vilker, [phone]; [e-mail].