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Author (up) Ahn, J.-E.; Zhu-Salzman, K. url  doi
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  Title CmCatD, a cathepsin D-like protease has a potential role in insect defense against a phytocystatin Type Journal Article
  Year 2009 Publication Journal of Insect Physiology Abbreviated Journal J Insect Physiol  
  Volume 55 Issue 8 Pages 678-685  
  Keywords Amino Acid Sequence; Animals; Aspartic Acid Endopeptidases/antagonists & inhibitors/chemistry/genetics/*metabolism; Beetles/chemistry/*enzymology/genetics/metabolism; Cathepsin D/chemistry/genetics; Cystatins/*metabolism/pharmacology; Cysteine Endopeptidases/chemistry/genetics/metabolism; Digestive System/chemistry/enzymology; Enzyme Inhibitors/*metabolism/pharmacology; Enzyme Stability; Gene Expression Regulation, Enzymologic; Insect Proteins/antagonists & inhibitors/chemistry/genetics/*metabolism; Molecular Sequence Data; Sequence Alignment; Soybean Proteins/*metabolism/pharmacology  
  Abstract When fed on a diet containing a proteinaceous cysteine protease inhibitor from soybean (scN), cowpea bruchid larvae enhance their overall digestive capacity to counter the inhibitory effect. Elevated proteolytic activity is attributed not only to the major digestive cysteine proteases (CmCPs), but also to aspartic proteases, a minor midgut protease component. In this study, we isolated a CmCatD cDNA from cowpea bruchid midgut that shares substantial sequence similarity with cathepsin D-like aspartic proteases of other organisms. Its transcript profile was developmentally regulated and subject to alteration by dietary scN. CmCatD transcripts were more abundant in scN-fed 3rd and 4th instar midguts than in control. The bacterially expressed recombinant CmCatD proprotein was capable of autoprocessing under acidic conditions, and mature CmCatD also exhibited pH-dependent proteolytic activity which was inhibited specifically by pepstatin A, indicative of its aspartic protease nature. CmCatD trans-activated CmCPs and vice versa, suggesting a cooperation between the minor midgut CmCatD and major digestive CmCPs. Further, CmCatD was able to degrade scN after extensive incubation. This activity partially restored CmCP proteolytic activity otherwise inhibited by scN. Thus CmCatD could facilitate insects' coping with the challenge of dietary scN by exerting its scN-insensitive and scN-degrading activity, freeing cysteine proteases for food degradation. Taken together, cowpea bruchids coordinate the functionality of the two classes of digestive proteases to fend off the negative effect of scN, and fulfill their nutrient requirements.  
  Address Department of Entomology, Texas A&M University, College Station, TX 77843, USA  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0022-1910 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:19446566 Approved no  
  Call Number HTU @ ammasino @ Serial 89  
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