Monitoring Key Reactions in Degradation of Chloroaromatics by In Situ 1 H Nuclear Magnetic Resonance: Solution Structures of Metabolites Formed from cis -Dienelactone

Abstract

ABSTRACT A 1 H nuclear magnetic resonance ( 1 H NMR) assay was used to study the enzymatic transformation of cis -dienelactone, a central intermediate in the degradation of chloroaromatics. It was shown that the product of the cis -dienelactone hydrolase reaction is maleylacetate, in which there is no evidence for the formation of 3-hydroxymuconate. Under acidic conditions, the product structure was 4-carboxymethyl-4-hydroxybut-2-en-4-olide. Maleylacetate was transformed by maleylacetate reductase into 3-oxoadipate, a reaction competing with spontaneous decarboxylation into cis -acetylacrylate. One-dimensional 1 H NMR in 1 H 2 O could thus be shown to be an excellent noninvasive tool for monitoring enzyme activities and assessing the solution structure of substrates and products.