SOLANUM PROTEASE INHIBITORS AND THEIR THERAPEUTIC POTENTIALITIES: A REVIEW

Protease inhibitors (PIs) are diverse group of proteins with low molecular weight that are ubiquitous in all life forms. PIs are reducers of the physiological activity of proteases and fascinated the attention of biotechnological researchers. In the evolutionary course, plants have developed diverse adaptive mechanisms of defence against various unfavorable conditions including that of predators and pathogens. Phylogenetic relationships among diverse PI families like serpin, Bowman–Birk, cereal trypsin/α-amylase inhibitor, proteinase inhibitor I, proteinase inhibitor II and cystatin have been evaluated. PIs evolution seems to occur through multiple interacting mechanisms and not commonly seen with other co-evolving molecules. Interaction of PIs produced by host organisms and the invasive/dietary protease of pathogens or parasites or predators, leads to a phylogenetic ‘arms race’ of rapid structural modulation in both interacting proteins. Further, the high rate of retention of gene duplication and inhibitory domain multiplication results the PI as potential model system to trace the basic evolutionary process of functional diversification. The mode of action of PI is either via inactivating the hydrolytic enzymes or depolarization of cell membrane of the pathogens thereby inhibiting its growth and invasion. Generally, PIs possess significant number of disulfide bonds due to cysteine residues that provide them resistance to heat, extremes of pH, and proteolysis. However, PIs have been extracted and purified only from few monocots and dicots plants. Currently, PI genes were used for developing insect-resistant transgenic plants for crop improvements. Classification of PIs over the last several years has been based on structural–functional relationships. This review bridges the gap between the folkloric uses of Solanum PIs, their diversity and biological potentialities.