Synthesis and hormonal activity of [Tyr22] glucagon and [desHis1, Tyr22] glucagon.
[Tyr22] glucagon and [desHis1, Tyr22] glucagon were synthesized by an improved solid phase procedure on a Pam-resin. The course of the synthesis was monitored by quantitative ninhydrin analysis and preview sequencing. Following cleavage by the low/high HF method the peptides were purified by ion exchange chromatography and reverse phase HPLC. The overall yield of homogeneous isolated peptide from the first amino acid was 41%. Circular dichroism measurements on dilute solutions in mixed aqueous organic solvents at pH 2, 6.9 and 9.2 showed increased beta-sheet structure relative to glucagon. [Tyr22] glucagon was a full agonist with 20-30% activity in the rabbit blood glucose assay and 10% activity in the rat liver membrane adenyl cyclase assay. [desHis1, Tyr22] glucagon had only a trace of activity in the adenyl cyclase assay (less than 0.002%) but bound to membranes in a competitive [125I] glucagon assay 1.0% as well as glucagon. The analog completely inhibited formation of cAMP by natural glucagon, with 50% inhibition at a ratio of 83:1 and pA2 = 6.7. The data are discussed in terms of models of glucagon structure in dilute solution.
Lu
G S
GS
Mojsov
S
S
Merrifield
R B
RB
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D002942:Circular Dichroism; D005934:Glucagon / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D007202:Indicators and Reagents; D008099:Liver / Q000201:enzymology; D011487:Protein Conformation; D011817:Rabbits; D051381:Rats; D013329:Structure-Activity Relationship
D001786:Blood Glucose; D007202:Indicators and Reagents; C053138:glucagon, des-His(1)-Tyr(22)-; D005934:Glucagon; C053137:glucagon, Tyr(22)-; D000262:Adenylyl Cyclases