Human brain GABA transaminase is immunologically distinct from those of other mammalian brains

Monoclonal antibodies (mAbs) to bovine brain gamma-aminobutyric acid (GABA) transaminase were characterized by epitope mapping analysis, and used as probes to compare the epitopes of the enzymes from several mammalian brains including man. From the epitope mapping analysis, three subgroups of mAbs recognizing different peptide fragments were identified. In the immunoblots probed with the mAbs, only one out of the three subgroups of mAbs reacted with a protein band of 50 kDa from human brain; the two other mAbs failed to detect any signal on the blots. In contrast, all of the mAbs did recognize a GABA-T protein band on immunoblots of all other mammalian brains tested. The results suggest that human brain GABA transaminase is immunologically distinct from those of other mammalian brains.