Substrate Diversity of Macrophomate Synthase Catalyzing an Unusual Multistep Transformation from 2-Pyrones to Benzoates

Macrophomate synthase, which we have recently purified, catalyzes an unusual multistep transformation from 5-acetyl-4-methoxy-6-methyl-2-pyrone to 4-acetyl-3-methoxy-5-methyl-benzoic acid (macrophomic acid). To investigate the substrate diversity of the enzyme, 40 analogs of 2-pyrone were prepared and their relative efficiency was examined in the enzymatic conversions. The experimental results reveal the structural requirements of the substrates and the rough size of the enzyme active site, and eliminate the ambiguity caused by contamination by other enzymes in the whole-cell experiments.