Pancreatic proteinases from man, trout, rat, pig, cow, chicken, mink and fox. Enzyme activities and inhibition by soybean and lima bean proteinase inhibitors.

1. The specific activities of the trypsins and chymotrypsins, measured with synthetic substrates, varied within one order of magnitude. 2. The trout trypsin and chymotrypsin were 5-15 times as efficient in hydrolyzing casein as the remaining animals. 3. The inhibition of total caseinolytic activity in extracts of pancreatic tissue by SBTI and inhibitors in crude extracts of raw soybeans varied ten-fold. 4. The animals may be ranked as follows according to the sensitivity of the caseinolytic activity to SBTI; trout greater than fox, chicken, greater than pig greater than rat, cow greater than mink greater than man.