Studies on Peptides.XIII.Contribution of the Arginine Residue in L-Histidyl-L-phenylalanyl-L-arginyl-L-tryptophyl-glycine to Its Melanotripic Activity

Abstract

Synthesis and melanotropic activity (expressed as MSH U/g.) of three pentapeptides, L-histidyl-L-phenylalanyl-L-ornithyl-L-tryptophylglycine (practically inactive), L-histidyl-L-phenylalanyl-L-lysyl-L-tryptophylglycine (1×10⁴) and L-histidyl-L-phenylalanyl-D-arginyl-L-tryptophylglycine (practically inactive) were reported and the physiological role of the arginine residue in L-histidyl-L-phenylalanyl-L-arginyl-L-tryptophylglycine(I), an active fragment of α-melanocyte-stimulating hormone (α-MSH) was discussed. In addition, MSH activity of D-histidyl-L-phenylalanyl-D-arginyl-L-tryptophylglycine (practically inactive) and L-histidyl-D-phenylalanyl-L-arginyl-D-tryptophylglycine (1×10⁶) was recorded and stereochemical nature of I was discussed in relation to the in vitro MSH activity.