Action of Thrombin on Ovine, Bovine and Human Pituitary Growth Hormones

Abstract

1 This communication reports the action of bovine thrombin on, ovine, bovine and human growth hormones. Thrombin cleavage was shown to be restricted to a single homologous peptide bond in all three growth hormones (at sequence positions 133–134 of the ovine and bovine hormones). 2 Ovine growth hormone was the most sensitive, to the action of thrombin, bovine growth hormone was attacked to a relatively less extent, and human growth hormone was the most resistant to the enzyme. 3 After reduction and carbamidomethylation of the disulfide bonds in thrombin modified ovine growth hormone, the two fragments (residues 1–133 and 134–191) were isolated. The large N H₂-terminal thrombin fragment of the hormone (residues 1 – 133) was found to be inactive in the rat tibia test, whereas a tryptic fragment (residues 96-133) isolated in an independent way gave measurable responses.