some properties of α-amylase in the digestive system and head glands of cryptolaemus montrouzieri (coleoptera: coccinellidae)

biochemical characteristics of α-amylase in the digestive system and head glands of cryptolaemus montrouzieri, a key predator of citrus mealybug, planococcus citri (pseudococcidae), were studied. the major isoform of α-amylase with the same molecular weight was detected in both gut and head glands loaded on polyacrylamide-starch gel electrophoresis. moreover, a minor band with much lower intensity was observed in zymogram analysis of gut. results showed that the specific activity of α-amylase from head glands (0.89 ± 0.02 μmol/min/mg protein) was significantly more than that of digestive system (0.76 ± 0.01 μmol/min/mg protein) in common condition (temperature equal to 25 ± 1 oc). the optimal ph and temperature for α-amylases activity were determined to be nearly 4 and 50°c in digestive system and 6 and 60 °c in head glands, respectively. edta (ethylenediamine tetra acetic acid), mg2+, na+, co2+, fe2+ and ca2+ inhibited the enzyme activity but ba2+, zn2+, hg+ and k+ enhanced enzyme activity in digestive system. edta and all tested metal ions except ba2+ inhibited the enzyme activity of head glands. detectable levels of α-amylase activity in the insect reflect adaptation of the coccinellid for using starch granules or sugars (honeydew; sugary excreta of homopterans; and nectar) as a source of food in addition to predatory habits.