EFFECT OF VARIOUS ACTIVATORS ON SALIVARY AMYLASE OF BUG LYGUS DISPONSI

The effect of various activators on the salivary amylase of Lygus disponsi was investigated. The salivary amylase was strongly activated by glutamine and moderately by asparagine, aspartic acid, and glutamic acid. The activating effect of glutamine at pH 7·0 began to appear at about 10-4 M of glutamine concentration, reaching a maximum at about 10-1 M. The activating effect of KNO3 at pH 7·0 began to develop at about 10-5 M of KNO3, reaching a maximum in the range 10-3 ∼10-1 M, and then decreased sharply. The activating effect of KNO3, as well as NaCl, increased linearly with the decrease in hydrogen-ion concentration and was even appreciable at pH 4·5-5·0, which was the optimum pH for the action of salivary amylase. In the presence of KNO3 or NaCl activity of the salivary amylase was extended over a wide pH range and the optimum pH was shifted from pH 4·5 to 5·0 to about pH 6·0. The activating effect of the mixture (NaCl+KNO3) was not in general given by the simple sum of the activating effect of each component. When one of the components was of such a concentration that, if used alone, it would exhibit maximum attainable activation, the effect due to the other component was completely masked, whereas when the concentration of each component was such that it produced an activating effect less than the maximum, both components in the mixture played the rôle of activators. Only when their individual activating powers were sufficiently small did their sum coincide with the observed value for the mixture. The salivary amylase was strongly to moderately activated by various plant extracts and the gut extract. The activating effect of the flower bud extract of rape at pH 7·0 appeared at an extract concentration of 10-3 to 10-4, reaching a maximum at about 7·5 × 10-2. It may be possible that NO3- and Cl- increase the rate of starch digestion in the gut and are useful for stabilizing the function of the amylase against the change of pH in the gut, and consequently play a part in extending the host range of L. disponsi. © 1969.