S-PEGYLTHIOPAPAIN, A VERSATILE INTERMEDIATE FOR THE PREPARATION OF THE FULLY ACTIVE FORM OF THE CYSTEINE PROTEINASE ARCHETYPE

Papain is widely used in several laboratories as a reference enzyme an d, as such, needs to be highly pure. A one-step purification of the en zyme is described here starting from spray-dried papaya latex. After p rotection of the essential SH group with a monomethoxypolyethylene gly col derivative synthesised in our laboratory, the mixture of papaya en zymes is submitted to fractionation on S-Sepharose Fast Flow. This pro cedure leads to the isolation of the S-pegylthiopapain conjugate devoi d of any contamination nor by the enzyme's irreversibly oxidized form nor by one of the other proteinases present in the original mixture. T hereafter, S-pegylthiopapain may be quite easily converted into its fu lly active form.