Detection of N-acetylated forms of beta-endorphin and nonacetylated alpha-MSH in the intermediate pituitary of the toad, Bufo marinus.
Steady-state analysis of the acid extracts of the intermediate pituitary of the toad, Bufo marinus, revealed the presence of multiple forms of beta-endorphin and alpha-MSH. Approximately 98% of the immunoreactive beta-endorphin was N-acetylated. The major form of N-acetylated beta-endorphin, which represented 81.5% of the total beta-endorphin recovered from this tissue, had an apparent molecular weight of 1.2 kDa and a net charge of +1 at pH 2.75. Approximately 98% of the immunoreactive alpha-MSH present in the Bufo intermediate pituitary had reverse phase HPLC properties similar to the nonacetylated form of alpha-MSH, ACTH(1-13)amide. These observations are in agreement with studies on the intermediate pituitary of the frog, Xenopus laevis, which have shown that the N-acetylation of alpha-MSH in this species is a cosecretory processing event, whereas the N-acetylation of beta-endorphin is a posttranslational processing event (2, 5, 15). These observations indicate that the N-acetylation of beta-endorphin and alpha-MSH occurs at distinct subcellular sites in intermediate pituitary cells of anuran amphibians. The Bufo intermediate pituitary will serve as a good model system for studying these novel N-acetyltransferase reactions.
Steveson
T C
TC
University of Denver, Department of Biological Sciences, CO 80208.
Jennett
C L
CL
Dores
R M
RM
D000107:Acetylation; D000818:Animals; D002024:Bufo marinus / Q000378:metabolism*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005260:Female; D008297:Male; D010902:Pituitary Gland / Q000737:chemistry*; D011863:Radioimmunoassay; D000521:alpha-MSH / Q000032:analysis*; D001615:beta-Endorphin / Q000032:analysis*
D000521:alpha-MSH; D001615:beta-Endorphin