Two modifications of a method are presented for assaying proteolytic enzymes. They differ primarily in the mechanism used for terminating the enzymic reaction, one technique employing trichloroacetic acid (TCA), the other, heat inactivation. Comparative studies reveal that there are two distinct disadvantages in using TCA which are not evident with the heat inactivation procedure. In the first place, TCA does not selectively precipitate residual substrate. Secondly, in the presence of acid, linear alkyl benzene sulfonate and other long chain anionic surfactants interfere with the quantitative determination of enzymic activity. This interference can be falsely interpreted as inhibition of proteolysis. An explanation of the above phenomena is given in the text along with assay results in the presence of metal chelating agents.
An automated biological assay for proteases in detergents was developed. The assay involved enzymic digestion of casein followed by the analysis of the liberated amino groups. Quantitative determination of the proteolytic activity was accomplished by reacting the amino groups with trinitrobenzene‐sulfonic acid (TNBS). An automated system was used to carry out both the digestion and the quantitative color development of the TNBS‐amino group complex. The method is accurate, reproducible, easy to handle, fast and free from interferences by any of the standard detergent ingredients. It may also be used as an investigative tool in enzyme research.
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