1] l-Glutamate decarboxylase from brain

Abstract

Publisher Summary γ-Aminobutyric acid (GABA) is one of the major neurotransmitters in the vertebrate central nervous system. L-Glutamate decarboxylase (GAD), which catalyzes α-decarboxylation of L-glutamate to form GABA and CO 2 , is the rate-limiting enzyme that normally determines the steady-state levels of GABA in vertebrate and invertebrate nervous systems. There is good correlation between GABA levels and GAD activity in vertebrate nervous system. Hence, GAD is a better marker for GABAergic neurons than GABA per se, which may redistribute or may be metabolized during the preparation of the tissues. This chapter discusses the various purification procedures, assay methods, and criteria of purity of GAD preparations. The immunochemical characterization of anti-GAD serum and immunocytochemical studies of GAD are also discussed. GAD is assayed by a radiometric method based on the formation of 14 CO 2 from either L-[1- 14 C] - or L-[U- 14 C] glutamate.