Fecal chymotrypsin: study on some characteristics of the enzyme.

A Lineweaver-Burk plot demonstrated that the apparent Michaelis constants are identical for chymotrypsin (CT) in duodenal juice and in feces of the same patient. CT in fecal homogenates exhibits exhibits a remarkable stability and is bound to particles to a considerable but variable extent. The pH optimum of CT in human feces is somewhat higher as compared to pure bovine pancreatic CT. All measurements of fecal CT activity should, therefore, be performed at pH 9.0. The distribution of CT among the fecal mass has been investigated. There were considerable differences between CT activities in random fecal specimens and in the corresponding stool collections. However, if the results were expressed in terms of 'normal' and 'abnormal', 113 out of 120 random fecal specimens gave the same results as the corresponding stool collections. It is concluded that the risk of 'false-normal' values cannot be effectively reduced by determination of CT outputs in stool collections (or by using continuous markers) instead of CT activities in random stool specimens.