Inhibition of Proteinase K by Mercury

Abstract

The serine protease Proteinase K from Tritirachium album Limber (PK) belongs to the subtilisin family, and contains 5 cysteine residues. Four of them form disulphide bridges while one, Cys 73, is in the reduced form¹. It has long been known that this enzyme is inhibited by inorganic mercury(II) but not, for example, by p-chloro-mercuribenzoate². Recently, it was shown that after reaction with Hg²⁺, PK can be reactivated by an excess of I^- or CN^- but not by Br^- or thiourea³.