Enzymes of glutamate system

Abstract

In this chapter, we discuss the role and methodological approaches for extraction and quantification of four major enzymes involved in human brain glutamate metabolism, glutamine synthetase (GS), glutamic acid decarboxylase (GAD), glutamate dehydrogenase (GDH), and phosphate-activated glutaminase (PAG). We describe their quantification in extracts of postmortem brain tissue from healthy subjects (controls) and patients with mental and neurodegenerative disorders. We discuss the presence of multiple isoforms for each of these enzymes. We detail the use of Western blotting with chemiluminescent enhancement of signal (ECL) as the most informative method for studying glutamate-metabolizing enzymes. Several examples are given for determining relative quantities of GS, GDH, GAD, and PAG in extracts from brain samples coming from various brain areas and obtained from control cases and subjects with schizophrenia and Alzheimer’s disease.