Studies on the digestive enzymes of the blowfly Calliphora erythrocephala. II. Kinetic constants of the larval gut proteinase

Abstract

1. 1. Sulfanilamide-azocasein is a suitable substrate for the quantitative estimation of larval blowfly gut proteinase. 2. 2. The pH-activity curve is similar to that of other blowfly larvae and the pH optimum of 7.8 corresponds closely to the pH of anterior midgut and posterior midgut contents. 3. 3. The velocity-substrate concentration relationship is typical. The K m value, obtained by a statistical and several graphical methods, corresponds to a substrate concentration of 7.19 × 10 −2 g/100 ml. 4. 4. Calliphora larval gut proteinase is partially inactivated after 24 hr at 37 °C and 44 °C, but for short periods of incubation (2 hr) the maximum activity is recorded at 44 °C. 5. 5. Over the range 5 °C to 35 °C the temperature-activity relationship follows the Vant-Hoff-Arrhenius equation. The activation energy, E A , is 13,060 cal/mole.