Diversity of glutamate dehydrogenase in human brain.

Three forms of glutamate dehydrogenase (GDH, EC 1.4.1.3) are purified from human brain tissue. Two of them, named GDH I (consisting of 58+/-1-kDa subunit) and GDH II (consisting of 56+/-1 -kDa subunit), are readily solubilized and the third one, GDH III (consisting of 56+/-1-kDa subunit), is a membrane-associated (particulate bound) isoform. Kinetic constants were determined for GDH III. These GDH forms were found to differ in hydrophobicity as indicated by different affinity to Phenyl-Sepharose. All three GDH forms showed microheterogeneity on two-dimensional (2-D) gel electrophoresis. Specific polyclonal antibodies, which enable to determine the levels of immunoreactivities of all the GDH forms in human brain extracts by enzyme-chemiluminescent amplified (ECL)-Western immunoblotting, were obtained.