Enzymological studies of melanotropins.
The relative stability of natural melanotropins and related synthetic analogues to serum and purified proteolytic enzymes was studied. Both alpha- and beta-MSH were rapidly inactivated by frog serum, but much more slowly by rat serum. beta-MSH was more stable than alpha-MSH to serum inactivation. Both alpha- and beta-MSH were rapidly inactivated by alpha-chymotrypsin and trypsin. The synthetic analogues, [Nle4, D-Phe7]-alpha-MSH and [Cys4, Cys10]-alpha-MSH, were totally resistant to inactivation by frog and rat serum enzymes. [Nle4, D-Phe7]-alpha-MSH was resistant to inactivation by alpha-chymotrypsin and trypsin, whereas [Cys4, Cys10]-alpha-MSH was partially resistant to these enzymes under similar conditions. Melanotropin analogues resistant to inactivation by serum enzymes may prove useful in a variety of physiological studies wherein natural melanotropins would be rapidly inactivated.
D000818:Animals; D002918:Chymotrypsin / Q000378:metabolism; D004798:Enzymes / Q000097:blood*; D009074:Melanocyte-Stimulating Hormones / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008968:Molecular Conformation; D011894:Rana pipiens / Q000097:blood; D051381:Rats; D014357:Trypsin / Q000378:metabolism; D000521:alpha-MSH / Q000031:analogs & derivatives*
D004798:Enzymes; C034542:MSH, 4-half-Cys-10-half-Cys-alpha-; D000521:alpha-MSH; C024146:MSH, 4-Nle-alpha-; C027756:MSH, 4-Nle-7-Phe-alpha-; D009074:Melanocyte-Stimulating Hormones; D002918:Chymotrypsin; D014357:Trypsin