ABSTRACT
A true -amylase was demonstrated from crude and partially purified extracts from whole carcasses of sweetpotato whiteflies (SPW) (Bemisia tabaci Genn.). All nymphal instars and adult SPW were found to have active -amylase, including newly enclosed crawlers that had not yet fed on plant materials. Protein-specific activities were greatest in 1st instars and decreased with age up to the "pupal" stage with a very slight increase in activity in adults. However, activity per individual did not differ substantially as a function of age. The -amylase had an apparent molecular weight of about 70 KD and an isoelectric point of 6.32. The enzyme activity was severely inhibited by EDTA and activated by NaCl and KNO3. CaCl2 also strongly enhanced activity. -Amylase activity was greatest at pH 7.0, but there was considerable activity at pH's below 7.0. Implications are discussed of the meaning of -amylase activity in an insect thought to be a phloem feeder.
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