Processing and Degradation of Met-Enkephalin by Peptidases Associated with Rat Brain Cortical Synaptosomes

Abstract

More than 20 peptides have been identified in neurones of the brain, spinal cord and in the periphery. There is growing evidence that some of these peptides act as neurotransmitters in the nervous system (for review see Hökfelt et al., 1980, Snyder, 1980, Konishi et al., 1981). The discovery of the enkephalins, Tyr-Gly-Gly-Phe-Met and Tyr-Gly-Gly-Phe-Leu, (Hughes et al., 1975) has led to numerous studies of their metabolism. For the regulation of the activity of these peptides the mode of processing from larger precursor proteins of peptides and of inactivation by proteolytic cleavage is of fundamental importance. Enkephalin containing polypeptides have been described in different organs such as adrenal medulla, intestine mucosa and brain (Lewis et al., 1979, Stern et al., 1981) as potential processing products of the larger pro-enkephalin precursor. The carboxyterminus of pro-enkephalin consists of the met-enkephalin-Arg⁶-Phe⁷ sequence (Gubler et al., 1982, Noda et al., 1982).