Direct observation of substrate distortion by triosephosphate isomerase using Fourier transform infrared spectroscopy

Abstract

The IR spectrum of dihydroxyacetone phosphate bound to [chicken muscle] triose phosphate isomerase was measured. There are 2 carbonyl bands corresponding to the bound substrate, with an intensity ratio of about 3:1. Relative to the carbonyl absorption of dihydroxyacetone phosphate in free solution, the major band is shifted by 19 cm-1 to 1713 cm-1, providing direct evidence of enzyme-induced distortion of the substrate. This strain is probably attributable to an enzymic electrophile that polarizes the carbonyl group of the substrate and thereby promotes catalysis.