Substance P and [Leu]enkephalin are hydrolyzed by an enzyme in pig caudate synaptic membranes that is identical with the endopeptidase of kidney microvilli.
The hydrolysis of [Leu]enkephalin and substance P by purified pig kidney endopeptidase (EC 3.4.24.11) and synaptic membranes prepared from pig caudate nuclei has been compared. The hydrolysis of an enkephalin analogue (Tyr-D-Ala-Gly-Phe-Leu) at the Gly-Phe bond was completely inhibited by phosphoramidon. The IC50 concentration (8 nM) was similar to that reported for [Leu]enkephalin hydrolysis by the purified endopeptidase [Fulcher, I. S., Matsas, R., Turner, A. J. & Kenny, A. J. (1982) Biochem. J. 203, 519-522]. Seven peptides were produced when substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2) was hydrolyzed by the kidney endopeptidase. These were formed by cleavage at bonds Gln-Phe (positions 6 and 7), Phe-Phe (positions 7 and 8), and Gly-Leu (positions 9 and 10). Synaptic membranes generated peptides with the same HPLC retention times and hydrolysis of substance P by either preparation was inhibited completely by 10 microM phosphoramidon. The most susceptible bond appeared to be Gly-Leu (positions 9 and 10). A specific polyclonal antibody raised in rabbits to purified pig endopeptidase inhibited the hydrolysis of [Leu]enkephalin and substance P by detergent-solubilized kidney microvilli or synaptic membranes; the titration curves were essentially identical. We conclude that the endopeptidase, which we suggest should be designated "endopeptidase-24.11," is present in caudate synaptic membranes and could play an important role in the hydrolysis of neuropeptides.[1]References
- Substance P and [Leu]enkephalin are hydrolyzed by an enzyme in pig caudate synaptic membranes that is identical with the endopeptidase of kidney microvilli. Matsas, R., Fulcher, I.S., Kenny, A.J., Turner, A.J. Proc. Natl. Acad. Sci. U.S.A. (1983) [Pubmed]
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