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Arthropods, 2020, 9(1): 7-14
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Article

Partial characterization of the digestive proteases and ¦Á-amylase of the larvae of the red palm weevil, Rhynchophorus ferrugineus

Ashraf Oukasha Abd El-latif
Department of Plant Protection, Faculty of Agriculture, Sohag University, Egypt

Received 23 December 2019;Accepted 10 January 2020;Published 1 March 2020
IAEES

Abstract
Activity of digestive enzymes (trypsin, chymotrypsin and ¦Á-amylase) in soluble protein extracted from the larval gut of Rhynchophorus ferrugineus was studied using specific substrates and enzyme inhibitors. Digestive enzyme activity showed a noticeable increase between day 5 and day 35. However, there was a noticeable decrease in the activity of trypsin protease on day 20. Maximum enzymes activity was observed at 40oC and pH of 8-9 in case of trypsin and chymotrypsin and pH 7-8 in case of ¦Á-amylase. Extract of digestive enzyme were incubated with different inhibitors specific for different classes of enzymes. SBTI and TPCK inhibited both trypsin and chymotrypsin like enzymes while could not inhibit ¦Á-amylase activity. EDTA and urea inhibitors could inhibit the activity of ¦Á-amylase but have no inhibition effect against trypsin and chymotrypsin enzymes. Kinetic analysis revealed higher Km value and higher Vmax value for the trypsin specific substrate (BApNA) compared with the chymotrypsin specific substrate (BTpNA). On the other hands, the Vmax value recorded for BApNA substrate was 11 times more than of that recorded for BTpNA substrate. The kinetic analysis of ¦Á-amylase like activity revealed that the enzyme has strong affinity to it substrate with moderate Vmax value. Results of the current study provide a fundamental knowledge that can be used to devise control strategies against R. ferrugineus.

Keywords Rhynchophorus ferrugineus;trypsin;chymotrypsin;¦Á-amylase;enzyme inhibitors.


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