A new unit for proteolytic activity determined by the modified ayre—Anderson method

Abstract

A unit of activity for proteolytic enzymes assayed by the modified Ayre-Anderson method has been defined in terms of the initial rate of production of trichloroacetic acid-soluble nitrogen. For proteinases acting on haemoglobin or gluten substrates, the relationship between activity and enzyme concentration is linear over a wide range, but for assay purposes initial reaction rates should be restricted to 10-20 mg N/h. For routine work the 'substrate constant' for a reaction system can be determined; this permits a single determination after a shorter time interval than required by the standard method, and allows the whole assay to be completed in one working day. The substrate constant must be determined for each set of reaction conditions, for each enzyme and, when a non-standardised substrate such as gluten is employed, for each batch of substrate. The method appears to be of greatest value for flours possessing normal levels of activity and for more active proteolytic preparations. It is only moderately accurate for flours having low activities.