Method of determination for proteases and antiproteases

A method for the determination of a protease which comprises reacting said protease with a substrate of the formula A-B, wherein A is N-substituted arginyl or a peptide having a C-terminal arginyl group and B is the residue of an amine electrolytically active amine, B-H, which can be oxidized or reduced electrochemically, whereby said amine is released from said substrate, and the determining the amount of amine which has been released by measuring an electric oxidation or reduction current passed between electrodes immersed in a medium containing said released amine, one of which electrodes is a pre-conditioned measurement electrode.