| Popis: |
1. 1. A peptidase which hydrolyses N- acetyl- l -phenylalanyl- l -tyrosine at an optimum pH of 4·I has been purified more than 500-fold from saline extracts of pig-thyroid glands. The procedure involves removal of thyroglobulin by acid precipitation followed by acetone fractionation and chromatography on DEAE-cellulose. 2. 2. Specificity studies on a variety of peptides at three pH values (pH 4·I, 5·3 and 7·2) indicated a requirement for at least one aromatic amino acid or leucine with the sole exception of l -methionyl- l -methionine which was hydrolysed to a slight extent. 3. 3. A comparison of the optimum pH of hydrolysis of the most susceptible substrates, N- acetyl- l -phenylalanyl- l -tyrosine , l -tryptophyl- l -leucine, glycyl- l -phenylalanyl- l -phenylalanine and glycyl- l -leucyl- l -tyrosine, showed slight differences in pH optima but all were within the range pH 4·I–4·9. |
