THE INHIBITION OF A LEAF PROTEINASE BY L-LYSINE HOMOPOLYMERS

The role of interlinked positively charged amino acids in the mechanis m of inhibition of a monomeric trypsin-like proteinase has been invest igated using high molecular mass L-lysine homopolymers ranging from 3. 8 to 109 kDa. The data show that the degree of polymerization enhances the inhibitory efficiency which is maximal for homopolymers with more than eighteen interlinked lysine residues. The inhibition is cooperat ive and, under the maximal inhibition conditions, nine lysine residues of the polymer are involved in the electrostatic binding to the enzym e. A limited conformational change of the protein molecule accompanies the transition from a fully active to a fully inactivated enzyme.