Brain Research, 68 (1974) 133-142 133 © ElsevierScientific Publishing Company, Amsterdam - Printed in The Netherlands IMMUNOCHEMICAL STUDIES OF BRAIN GLUTAMATE DECARBOXYLASE AND GABA-TRANSAMINASE OF STRAINS OF MICE SIX INBRED ESTHER WONG, ARNE SCHOUSBOE*, KIHACHI SAITO, JANG-YEN WU AND EUGENE ROBERTS Division of Neurosciences, City of Hope National Medical Center, 1500 E. Duarte Rd., Duarte, Calif 91016 (U.S.A.) (Accepted August 31st, 1973) SUMMARY Six different inbred strains of mice (C57BL/6J, CBA/CaJ, CE/J, DBA/2J, LP/J and RF/J) were compared in terms of specific activities and immunochemical proper- ties of brain L-glutamate decarboxylase (GAD) and ~,-aminobutyrate transaminase (GABA-T), the enzymes responsible for the synthesis and degradation of GABA, respectively. GAD from the brains of the different strains was indistinguishable on the basis of specific activities, double diffusion tests, immunoelectrophoresis and inhibi- tion by antibody. However, microcomplement fixation tests showed GAD from DBA and C57BL mice to be most distinctly different from GAD extracted from the Swiss mouse, from which the original antigen was prepared and that the enzyme from the CE, LP and RF also differed. Similar fixation curves were obtained for the GAD from CBA and Swiss mice. GABA-T from the different strains was indistinguishable on the basis of all the tests employed. INTRODUCTION In recent studies of the species specificity of the two GABA-metabolizing enzymes in brain, L-glutamic acid decarboxylase (GAD, E.C. 4.1.1.15) and ?-amino- butyrate-a-ketoglutarate transaminase (GABA-T, E.C. 2.6.1.19) it was shown that, in general, they seemed to follow a similar evolutionary pattern 17,18. In the present report the above two brain enzymes from different strains of * Present address: Universityof Copenhagen, Department of BiochemistryA, Juliane Mariesvej 30, 2100 Copenhagen, Denmark.