A unified assay for six enzymes of glutamate metabolism.

A single assay system has been developed for six enzymes of glutamate metabolism: glutamate dehydrogenase, glutaminase, asparate aminotransferase, γ-aminobutyrate aminotransferase, alanine aminotransferase, and glutamate decarboxylase. The first five are assayed by coupling them to Escherichia coli glutamate decarboxylase and measuring the release of ¹⁴CO₂ from radioactive substrates. Glutamate decarboxylase is assayed directly. The assays are simple, use but one technique, and require very little working time. At a reasonable cost per assay, they are considerably more sensitive than other commonly used assays for the same enzymes. The sensitivity of the assay at a fixed price increases as the substrate concentration decreases.