A radioactive method for the measurement of trypsin and trypsin-like activities

A simple and highly sensitive method for the assay of trypsin has been developed by making use of the phosphorylated synthetic peptide Leu-Arg-Arg-Ala-Ser-(32P)-Leu-Gly as substrate. The technique has been adapted from the phosphocellulose method of R. Roskoski, Jr. (in Methods in Enzymology (Corbin, J., and Hardman, J., Eds.), Vol. 99, pp. 3-6, Academic Press, New York) used for measuring of protein kinases. In addition to measuring the activity of trypsin at the microgram level, the 32P-labeled peptide method can be used for measuring other trypsin-like enzymes. It has been successfully utilized for the identification of a new peptidase from the fungus Saccobolus platensis.