Total synthesis of crystalline glucagon by the method of solid phase condensation of fragments. Protein Synthesis Group, Shanghai Institute of Biochemistry, Academia Sinica.
Looking back at the experiences of our own and of others in the past decade or so on the total synthesis of proteins and polypeptides, we have analyzed the inherent contradictions of the two alternative methods of synthesis on the basis of the dialectical viewpoint of "one dividing into two". Either the solid or the liquid-phase synthesis is fraught with difficulties when the target exceeds 100 amino acid residues. A new synthetic strategy has been developed which we believe can resolve the contradictions inherent in the synthesis of larger peptides--the solid phase stepwise condensation of peptide fragments instead of amino acids. Following repeated practice guided by the spirit of independence and self-reliance, we have succeeded in synthesizing first of all a new supporting resin layer which provisionally meets our requirements. We shall describe in the present paper the successful total synthesis of the nonacosapeptide glucagon using this supporting resin layer. Four peptide fragments (5, 6, 9, 6), synthesized with the aid of classical methods, have been coupled stepwise to a resin-bound tripeptide, with an efficiency of over 95% for each step. After treatment with hydrogen fluoride and purification twice by means of column chromatography, rhombic dodecahedral crystals of glucagon have obtained which are identical with natural products in respect of amino acid compositions, chromatographic and disc-electrophoretic behaviour, etc. The overall yield is about 17%. In view of the characteristic abundance in glucagon of various kinds of functional groups which form unfavourable obstacles to the course of synthesis, this relatively high yield and the ease with which crystalline products can be obtained testify to the potential of the new technique in the eventual total synthesis of larger proteins.
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D005934:Glucagon / Q000138:chemical synthesis* / Q000494:pharmacology; D008722:Methods; D011817:Rabbits
D001786:Blood Glucose; D005934:Glucagon