Biotechnology and Molecular Biology Reviews Vol. 2(3), pp. 068-085, August 2007
ISSN 1538-2273 © 2007 Academic Journals

Standard Review
 

Plant protease inhibitors: a defense strategy in plants

Huma Habib and Khalid Majid Fazili*

Department of Biotechnology, The University of Kashmir, P/O Naseembagh, Hazratbal, Srinagar -190006, Jammu and Kashmir, India.

Corresponding author. E-mail: fazili@kashmiruniversity.net or khalid_fazili@yahoo.com

. Phone: 009419003881; +91-194-2102154; Fax: +91-194-2428723.

Accepted 7 July, 2007

Proteases, though essentially indispensable to the maintenance and survival of their host organisms, can be potentially damaging when overexpressed or present in higher concentrations, and their activities need to be correctly regulated. An important means of regulation involves modulation of their activities through interaction with substances, mostly proteins, called protease inhibitors. Some insects and many of the phytopathogenic microorganisms secrete extracellular enzymes and, in particular, enzymes causing proteolytic digestion of proteins, which play important roles in pathogenesis. Plants, however, have also developed mechanisms to fight these pathogenic organisms. One important line of defense that plants have to fight these pathogens is through various inhibitors that act against these proteolytic enzymes. These inhibitors are thus active in endogenous as well as exogenous defense systems. Protease inhibitors active against different mechanistic classes of proteases have been classified into different families on the basis of significant sequence similarities and structural relationships. Specific protease inhibitors are currently being overexpressed in certain transgenic plants to protect them against invaders. The current knowledge about plant protease inhibitors, their structure and their role in plant defense is briefly reviewed.

Key words: Proteases, enzymes, protease inhibitors, serpins, cystatins, pathogens, defense.