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.
D000818:Animals; D002421:Caudate Nucleus / Q000201:enzymology*; D010450:Endopeptidases / Q000276:immunology / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000378:metabolism*; D007118:Immunoassay; D007668:Kidney / Q000201:enzymology; D008871:Microvilli / Q000201:enzymology; D013373:Substance P / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine; D013570:Synaptic Membranes / Q000201:enzymology; D009626:Terminology as Topic
D013373:Substance P; D004743:Enkephalin, Leucine; D010450:Endopeptidases