ABSTRACT
The search for peptidases in brain tissues which may be involved in the inactivation of neuropeptides has been strongly influenced by our knowledge of the inactivation of the cholinergic neurotransmitter acetylcholine by acetylcholinesterase in the vicinity of the synaptic junction. The search for peptidases which may be physiologically significant participants in the termination of neuropeptide activity has been influenced by the possibility that they may be acting as neurotransmitters at synapses and by knowledge of the enzymic inactivation of some classical transmitters such as acetylcholine. One of the more striking differences between the results obtained with whole animal experiment and those obtained with either membrane enriched particulate fractions or with cultured spinal cord cells concerns the nature of the enzyme converting angiotensin II to angiotensin III. A different picture of angiotensin II metabolism emerged from a study on the inactivation of this peptide by cultured mouse spinal cord cells.
