Abstract
A method is described for the quantitative histochemical determination of dehydropeptidase I based upon the spectrophotometric procedure of Carter and Greenstein (1946). The method will measure enzyme activity in most tissues with samples of 30 to 50 µg dry weight. In a very active tissue such as kidney only 10 µg are required. Absolute ethanol has been suitable for precipitating protein and reducing the blank. Multiple determinations on the same tissue sample show good agreement, with coefficients of variation of less than 8. Optima for incubation time and tissue concentration are described.