Isolation and characterization of alpaca growth hormone

A simple and mild procedure is described for the isolation of pituitary growth hormone from alpaca glands. It involves extractions in buffer at pH 8.7 and gel filtration in Sephadex G-75. an average yield of 1 mg purified product may be obtained from 1 g fresh alpaca pituitary glands. The alpaca hormone was examined for homogeneity by SDS-polyacrylamide gel electrophoresis, gel electro-focusing and end-group analyses. It is a protein composed of a single polypeptide chain with phenylalanine at both ends. The C-terminal sequence is -Ala-Phe. The molecular weight is approximately 21 700 and the amino acid composition very similar to that observed in equine growth hormone.