Human pituitary growth hormone: a biologically active hendekakaihekaton peptide fragment corresponding to amino-acid residues 15-125 in the hormone molecule.

A hendekakaihekaton peptide fragment has been prepared by cyanogen bromide cleavage of the NH2-terminal 134-residue fragment of human pituitary growth hormone. It was characterized by amino-acid and end-group analyses, exclusion chromatography, disc electrophoresis, circular dichroism, and ultracentrifugation. The fragment, corresponding to amino-acid residues 15-125 in the hormone molecule, possesses hepatic ornithine decarboxylase (EC 4.1.1.17; L-ornithine carboxy-lyase) stimulating, lactogenic, and somatotrophic activity. It has immunoreactivity in the microcomplement-fixation and radioimmunoassay experiments. The circular dichroism data indicate that the hendekakaihekaton peptide fragment is devoid of secondary and tertiary structure.