Effect of calcium ions on the processing of pro-opiomelanocortin by bovine intermediate lobe pro-opiomelanocortin-converting enzyme.
The effect of Ca2+ on the extent and pattern of processing of pro-opiomelanocortin and an N-terminal fragment by a purified pituitary secretory vesicle, soluble aspartic endoprotease, was studied. Ca2+ stimulated the first cleavage of pro-opiomelanocortin by pro-opiomelanocortin-converting enzyme to yield 21-23 kDa adrenocorticotropin and beta-lipotropin, but its effect was minimal. The production of adrenocorticotropin from the 21-23 kDa intermediate was stimulated approximately 2.3-fold in the presence of 10 mM Ca2+, and processing of beta-lipotropin to beta-endorphin was stimulated about 1.3-1.4-fold by 5-10 mM Ca2+. The production of gamma-melanotropin-immunoreactive material from bovine N-pro-opiomelanocortin(1-77) was stimulated approximately 1.3-fold at both 100 microM and 1.5-2.0 mM Ca2+. Further characterization of the gamma-melanotropin-immunoreactive material by HPLC demonstrated that the major products were gamma 3-[Lys]melanotropin and gamma 3-melanotropin at both Ca2+ concentrations. These results indicate that pro-opiomelanocortin-converting enzyme is stimulated by Ca2+.
Birch
N P
NP
Section of Cellular Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.
Bennett
H P
HP
Estivariz
F E
FE
Loh
Y P
YP
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D010450:Endopeptidases / Q000378:metabolism*; D006031:Glycosylation; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism; D010902:Pituitary Gland / Q000201:enzymology*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D043484:Proprotein Convertases; D001615:beta-Endorphin / Q000378:metabolism; D008083:beta-Lipotropin / Q000378:metabolism
D010446:Peptide Fragments; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D008083:beta-Lipotropin; D010450:Endopeptidases; D043484:Proprotein Convertases; D002118:Calcium