Proteolytic enzymes of Penicillium janthinellum

• 1.

  1. The properties of an extracellular peptidase (peptidase B) of Penicillium janthinellum which was separated by paper electrophoresis from a preparation of peptidase A, have been studied.

• 2.

  2. Unlike peptidase A, peptidase B will not activate trypsinogen.

• 3.

  3. Peptidase B is active on a number of peptides, none of which are substrates for peptidase A. Peptidase B is especially active on Cbz-l-glutamyl-l-phenylalanine, Cbz-l-glutamyl-l-tyrosine and Cbz-l-tyrosyl-l-glutamic acid, and while inactive on Cbz-glycyl-l-phenylalanine, it promotes hydrolysis of the free dipeptide glycyl-l-phenylalanine.

• 4.

  4. The hydrolysis of Cbz-l-glutamyl-l-tyrosine by peptidase B takes place optimally at pH 4.7. The extent of inhibition imposed by a range of anions on this hydrolysis has been recorded, and the effect of selected inhibitors on the kinetics of the reaction studied. The inhibition imposed by salts of the fatty acid series is proportional to the molecular weight of the inhibitor.

• 5.

  5. None of a series of metal salts tested increased the activity of the enzyme, and ferric, cadmium and barium ions were inhibitory.

• 6.

  6. The enzyme is not inhibited by sulfhydryl reagents.

• 7.

  7. A value for K_m of 5·10⁻⁴ M of Cbz-l-glutamyl-l-tyrosine was obtained.