Immunochemical comparisons of vertebrate glutamic acid decarboxylase

Antisera tol-glutamate decar?ylase (GAD) purified from mouse brain were produced in rabbits and the species specificities of GAD were examined. Antibodies to mouse enzyme were found to cross-react with the decar?ylases from brain of rat, human, calf, rabbit, guinea pig, frog, pigeon and quail in double diffusion tests. Trout enzyme did not cross-react. The decar?ylases from mouse and rat brain were inhibited to the extent of 50% and 35%, respectively, by anti-GAD IgG. The glutamate decar?ylases from other species were inhibited only slightly. Microcomplement fixation tests showed that the mouse, rat and human enzymes were quite similar. The results indicated that the rat enzyme is most closely related to the mouse enzyme, followed in order by human, rabbit, calf, guinea pig, pigeon, quail, frog and trout.