Brain aryl acylamidase

1. The serotonin (5-HT) sensitive brain aryl acylamidase (AAA) has received considerable attention due to its potential involvement in 5-HT action mechanism in CNS. 2. Multiple forms, AAA-1 and 2, have been separated by ammonium sulfate precipitation of brain extract and subsequent gel filtration. 3. Their chemical properties have been characterized and differentiated by effects of several classes of drugs including d-LSD, 5-HT, 5-HT related compounds and tetrahydro-beta-carbolines on their enzyme activities. 4. In the rat brain, AAA-1 shows highest specific activity in corpus striatum and lowest activity in cerebellum whereas AAA-2 shows highest specific activity in cerebellum and lowest activity in corpus striatum. 5. Subcellularly, AAA-1 exhibits highest specific activity in synaptosomal fraction of rat corpus striatum, lowest activity in mitochondrial fraction and no activity in nuclear fraction while AAA-2 exhibits highest specific activity in microsomal fraction and lowest activity in nuclear fraction. 6. Triton X-100 treatment altered the subcellular distribution pattern of both AAA-1 and AAA-2. 7. AAA-2 is possibly associated with true acetylcholinesterase (AChE) in brain based on its inhibition by neostigmine but its identity with AChE needs further elucidation. 8. To determine the physiological role(s) for brain AAA, naturally occurring aromatic alkylamines other than melatonin need to be tested as possible substrate(s) for the enzyme activity.