Specifically deuterated l-malate as an NMR probe of the aspartate transcarbamylase catalytic site

Abstract

Replacement of protons by deuterium at specific positions of l-malate results in simplified proton magnetic resonance spectra and a large reduction in the effect of intramolecular dipole-dipole relaxation of the proton resonances. Under conditions of concomitant deuterium decoupling, these spectra are further simplified. These advantages are used to study the proton relaxation of two specifically deuterated l-malates in the presence of the catalytic subunit of aspartate transcarbamylase. The bound relaxation rates of the deuterated L-malates are much smaller than those of undeuterated l-malate implying that the major relaxation mechanism for enzyme bound, undeuterated l-malate is the intramolecular dipole-dipole interaction.