Acetylation of alpha MSH and beta-endorphin by rat neurointermediate pituitary secretory granule-associated acetyltransferase.
ACTH(1-8) and ACTH(9-13)NH2 were used as potential enzyme inhibitors to begin examining the relationship between the acetylation of ACTH- and beta-endorphin-related peptides. ACTH(1-8) was a potent inhibitor of the acetylation of both ACTH- and beta-endorphin-related peptides, whereas ACTH(9-13)NH2 was an effective inhibitor only of the acetylation of ACTH-related substrates. This inhibition pattern indicated that there may be an unusual interaction between some ACTH- and beta-endorphin-related peptides as substrates for the acetyltransferase. Utilizing HPLC to separate ACTH- and beta-endorphin-related peptides present in the same reaction mixture, ACTH(1-14) and beta-endorphin(1-27) at Km and saturating concentrations were used as substrates to examine the ability of one peptide substrate to affect the acetylation of the other. It was observed that the acetylation of ACTH(1-14), even at Km concentration, was relatively unaffected by the presence of beta-endorphin(1-27). However, the acetylation of beta-endorphin(1-27) was significantly reduced by the presence of ACTH(1-14). This preferential acetylation of ACTH-related peptides over the acetylation of beta-endorphin-related peptides might have physiological importance under some conditions.
D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives; D000818:Animals; D002458:Cell Fractionation; D003594:Cytoplasmic Granules / Q000201:enzymology*; D004723:Endorphins / Q000378:metabolism*; D007700:Kinetics; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D010902:Pituitary Gland / Q000201:enzymology*; D051381:Rats; D013379:Substrate Specificity; D001615:beta-Endorphin
D004723:Endorphins; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D000123:Acetyltransferases