Oxidation of methionine residues in bovine growth hormone by chloramine-T

The methionine residues in bovine growth hormone were chemically modified wih chloramine-T at pH 7.4 using different chloramine-T methionine molar ratios. Methionine 4 was shown to be the most reactive followed in decreasing order by methionines 148, 123 and 178. With a 50-fold molar excess of chloramine-T over methionine almost full oxidation of all the methionine residues was achieved. The oxidation of the four residues of methionine does not change the growth promoting activity of the hormone.