Analysis of the Glutamate Decarboxylase Reaction by Membrane Inlet Mass Spectrometry

Summary

Membrane inlet mass spectrometry was used to investigate the pH dependence of two phases in the decarboxylation of glutamate by glutamate decarboxylase from Escherichia coli. Continuous assay of CO₂ production was used to determine the pH dependence of the steady state of the reaction. A transient resulting in activation of the enzyme when the pH was rapidly reduced was also studied by stopped-flow mass spectrometry. The results are interpreted in terms of a model based on cooperative interactions in this hexameric enzyme.