Inhibitory activity against papain, a CA1 cysteine peptidase, in Saccharomycetaceae

A search for new biological sources of cysteine peptidase inhibitors has not only an academic aspect but is of great importance in medicine and biotechnology. The activity of CA1 peptidases can be inhibited by proteins of nine structurally different families. Although these inhibitors are widespread in nature, there is little information on them in yeast and in the kingdom of fungi overall. To gain insight into the endogenous inhibitors of CA1 cysteine peptidases in unicellular fungi, we initiated a study of the extra- and intracellular antipapain activity in yeast. We report here, for the first time, an analysis of the inhibitory activity against papain in the culture medium and the cell-free extract of 16 yeast strains belonging to the Saccharomycetaceae family. The existence of the antipapain activity, likely from protein inhibitors, in all the tested yeast strains has been demonstrated.