Effects of three peptidase inhibitors, amastatin, captopril and phosphoramidon, on the hydrolysis of [Met5]-enkephalin-Arg6-Phe7 and other opioid peptides
作者:Toyokazu Hiranuma、K. Kitamura、Takao Taniguchi、Tomomi Kobayashi、Raita Tamaki、Masayuki Kanai、Kazuhito Akahori、Kayoko Iwao、T. Oka
DOI:10.1007/pl00005168
日期:1998.3.10
The contents of [Met(5)]-enkephalin-Arg(6)-Phe(7) (met-enk-RF) and its six hydrolysis products: Y, YG, YGG, YGGE YGGFM, and YGGFMR were estimated after incubating met-enk-RF with either a guinea-pig ileal or striatal membrane fraction for various times at 37 degrees C, After 45 min incubation with either ileal or striatal membranes, met-enk-RF was completely hydrolyzed, yielding Y as the major product. Incubation with either membrane preparation for 60 min in the presence of the aminopeptidase inhibitor amastatin hydrolyzed 90 or 92% of met-enk-RF, respectively, with YGG being the major product. If the dipeptidyl carboxypeptidase I inhibitor captopril is also included in the incubation, met-enk-RF hydrolysis decreases by about half for both membranes, with YGG remaining the major product. Inclusion of three peptidase inhibitors, amastatin, captopril, and phosphoramidon (inhibition of endopeptidase-24.11) further reduced met-enk-hydrolysis, with 87% or more remaining intact. This shows that met-enk-RF was mainly hydrolyzed by three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I and phosphoramidon-sensitive endopeptidase-24.11, in both ileal and striatal membranes.Additionally, estimations of [Leu(5)]-enkephalin (leu-enk), alpha- and beta-neoendorphins (alpha- and beta-neoends), and dynorphin B (dyn B) contents after incubating the individual peptides with striatal membrane for 60 min in the presence of the three peptidase inhibitors showed that 98, 32, 5, and 23%, respectively, remained intact.Our previous studies together with the data obtained here show that one group of endogenous opioid peptides: met-enk, leu-enk, met-enk-RF, met-enk-RGL, and dyn A-(1-8) are largely or almost exclusively hydrolyzed by the three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I, and phoramidon-sensitive endopeptidase-4.11, and indicate that an unidentified fourth enzyme(s) is involved in the hydrolysis of another group of peptides: alpha-neoend, beta-neoend, and dyn B.