Determination of the activity of proteases

A method and apparatuses for determining the total content of proteases by means of measuring their enzyme activity after previous deinhibition is disclosed. In biological samples, lysosomal proteases are completely (e.g. in blood serum) or partly (e.g. in tissue homogenates) inhibited. A method proposed for the deinhibition entails immersing a solid support material (e.g. nylon or nitrocellulose) as plastic strip to which is linked, covalently or by adsorption, an inhibitor-binding substance which binds the inhibitor corresponding to the protease more strongly than the protease in the sample for measurement. After the deinhibition has taken place, the plastic strip is removed from the liquid sample for measurement, and the sample for measurement is passed on for measurement of the enzyme activity. Fluorogenic substrates from which the fluorogen 7-amino-4-trifluoromethylcoumarin is eliminated proved to be particularly advantageous for the activity measurement. These substrates make it possible for the sensiti