Participation of amino groups in lipolytic action of growth hormone.

Abstract

Wepreviously reported that a fragment, A-II, isolated from a tryptic digest of bGHretained significant amounts of growth-promoting activity in rats and in vitro metabolism-stimulating activity in adipose tissue of hypophysectomized rats.1)2) It has also been demonstrated that A-II shows metabolic activities in humans similar to hGH.3>4) Since A-II is a peptide originating from the 96-133 portion ofbGH and has a structure similar to those of 96-133 ofoGH and 95-133 ofhGH and hCS, it has been suggested that the 96-133 segment of GH contains a structure essential for the GH activity.1>5) However, the amino acid residue or residues responsible for the GH activity remains unknown.In this paper, we present evidence that amino groups in bGHand A-II are closely associated with in vitro GH-induced lipolysis in fat cells isolated from rat epididymal adipose tissue. bGH was a generous gift from Dr. Sonenberg (Sloan-Kettering Institute for Cancer Research, N.Y.). A-II was prepared as previously reported.1* Acetic anhydride and sodium acetate were obtained from Nakarai Chemicals Ltd., Osaka. All other chemicals were of reagent grade.

Correlation of the Lipolytic Action of Synthetic Peptides with Their Structures: Importance of Acidic and Basic Amino Acid Residues in the N-Terminal Region

“…In this study, we showed that replacement of Arg-Glu by Lys-Asp led to a decrease in potency of the lipolytic action and that blocking the free guanidino group of Arg with nitro group resulted in loss of FF A release (Table II). Yamasaki et al 7 ) reported that blocking the free amino group of bovine growth hormone with an acetyl group caused a marked decrease in potency of its lipolytic action. These results suggest that a free guanidino or amino group may be important for a lipolytic action on fat cells.…”