Regional and Subcellular Distribution of Homocarnosine–carnosine Synthetase in the Central Nervous System of Rats

Homocarnosine–carnosine synthetase and carnosinase were assayed in homogenates, 100,000 g supernatants, and ammonium sulfate fractions of the supernatants from nine regions of the central nervous system (CNS), as well as subcellular fractions of whole brains. The enzymes were detected in all CNS regions tested, with olfactory bulbs having the highest activities of both enzymes. In the subcellular fractions, the synthetase was found mainly in the cell‐sap; carnosinase was detected in all fractions, the highest activity being in the mitochondria. The synthetases from olfactory bulbs, cerebellum and spinal cord have similar Km's for β‐alanine and GABA.