Bongers J, Offord R E, Felix A M, Campbell R M, Heimer E P
Department of Peptide Research, Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey.
Int J Pept Protein Res. 1992 Sep-Oct;40(3-4):268-73. doi: 10.1111/j.1399-3011.1992.tb00301.x.
Human growth hormone-releasing factor, GRF(1-44)-NH2, was synthesized by trypsin catalyzed coupling of Leu-NH2 to Arg43 of the precursor, GRF(1-43)-OH, prepared by solid phase peptide synthesis. The semisynthetic GRF(1-44)-NH2 was fully characterized and showed full potency in the rat pituitary in vitro bioassay. Conversion to GRF(1-44)-NH2 was limited to 60-70% in both 75% v:v N,N'-dimethylacetamide and 95% v:v 1,4-butanediol due to competing transpeptidations at Arg41 and Arg38 generating [Leu42]-GRF(1-42)-NH2 and [Leu39]-GRF(1-39)-NH2 side-products, respectively. The rates of formation and yields of GRF(1-44)-NH2 versus pH, Leu-NH2 concentration, and solvent composition were also studied.
