Metabolism of histamine in the CNS of Aplysia californica: cellular distribution of gamma-glutamylhistamine synthetase.
1. The cellular distribution of the histamine-metabolizing enzyme, gamma-glutamylhistamine synthetase, was studied in the CNS of Aplysia californica. 2. Enzyme activity was assayed in single, re-identifiable neuronal cell bodies, clusters of nerve cells and neuropil and capsule tissue surrounding the ganglia. 3. The "histaminergic" C-2 cells and all other single nerve cell bodies contained measurable gamma-glutamylhistamine synthetase activity. 4. The cerebral E cluster, which houses the C-2 cells and several of its post-synaptic neurons, had an apparently higher specific enzyme activity than other neuronal clusters. 5. The finding of measurable enzyme activity in the histamine-rich C-2 cell bodies and in clusters of cells responsive to this imidazoleamine supports the hypothesis that one function for gamma-glutamylhistamine synthetase is in the disposal of neuronally released histamine. 6. The average specific activity of gamma-glutamylhistamine synthetase in single cells was 3.64 +/- 0.32 mumol g protein hr. This represented only 5% of the enzyme activity measured in the whole ganglion. 7. The bulk of synthetase activity was found to reside in the capsule tissue.
D000818:Animals; D001048:Aplysia / Q000201:enzymology*; D002490:Central Nervous System / Q000201:enzymology*; D006632:Histamine / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology; D009928:Organ Specificity; D010453:Peptide Synthases / Q000378:metabolism*
D006632:Histamine; D010453:Peptide Synthases; C035550:gamma-glutamylhistamine synthetase