Isolation, Purification and Characterization of Equine Growth Hormone

Abstract

1 A simple and mild procedure is described for the isolation of equine growth hormone from frozen pituitary glands: it involves water extractions of the glands at pH 7.2 and 9.5, fractionation by ammonium sulfate precipitation and gel nitrations on a Sephadex G-100 column. The yield is 1.7 mg growth hormone per gram of fresh glands with a biological specific activity of 1.6 USP units/mg. 2 The protein obtained is homogeneous judged by disc electrophoresis, ultracentrifugation, gel electro focusing, gel filtration and end-group analyses. 3 A weight-average molecular weight of 20200 was determined by sedimentation equilibrium analysis. Comparative values were found by gel electrophoresis and exclusion chromatography. Its Stokes radius and frictional ratio were 2.25 nm and 1.21, respectively. 4 The amino acid composition of equine growth hormone shows considerable analogy with those of bovine, ovine and porcine growth hormones.