br Introduction Diverse types of protease inhibitors PIs hav
Introduction Diverse types of protease inhibitors (PIs) have been isolated, characterized, and evaluated for their biological potentials. They are small molecular mass peptides capable of inhibiting endogenous proteases. Plant PIs fascinates the attention of researchers because of their increasing use in pharmaceutical and biotechnological industries. In the course of evolution, plants have evolved adaptive mechanisms that provide them significant resistance against diverse kinds of unfavorable conditions including insects and phytopathogens. The mode of action of PI is either via inactivating the hydrolase enzymes or depolarization of plasma membrane of the pathogens thereby inhibiting its growth and invasion. PIs are diverse viz., rice cysteine PIs, potato serine PIs, cowpea serine PIs, sweet potato PIs, corn cystatins, soybean kunitz PIs, tobacco PIs, bean α-amylase inhibitors and mustard trypsin inhibitors. Some are trailed for producing transgenic insect resistant plants. Ussuf et al.  produced transgenic tobacco plant with CPTI gene from cowpea. In addition, PIs have long been treated as antinutritional and therefore, reviewed their possible role as antimetastatic and antiinflammation. Syed Rakashanda et al.  isolated and characterized serine protease inhibitor (LC-PI-I) from Lavatera cashmeriana seeds. It showed bactericidal potential against urinary tract infection, pneumonia and septicemia in humans. PIs were also employed as potential drugs in antiretroviral combination therapy which increases the expectancy in HIV patients . Satheesh and Murugan  also revealed the remarkable microbicidal potentiality of PIs from the leaves of Coccinia grandis against Klebsiella pneumoniae and Aspergillus flavus. Structurally, PIs belongs to diverse classes such as serine proteases, cysteine proteases, aspartate proteases and metalloproteases based on the active amino buy 69 8 that was seated in the reaction centers. The most extensively analyzed protease inhibitors in plants were serine and cysteine protease inhibitors. Eight groups of plant serine protease inhibitors were reported based on their amino acid sequences . Soybean trypsin inhibitor (SKTI), protease inhibitor 1 (PIN1) and protease inhibitor 2 (PIN2) families were well studied among them. PIN2 family consists of four groups such as Kunitz, Bowman Birk, Potato I and Squash families. PIN2 enzymes show wound-inducible expression patterns in leaves and constitutive expression in flowers . Meulenbroek et al.  purified and characterized double-headed heterodimeric serine PI of Kunitz-type from Solanum tuberosum. Most of the serine PIs have been isolated and characterized from Fabaceae, Cucurbitaceae, Solanaceae, Euphorbiaceae and Poaceae families. There are only limited works of purification and characterization of these inhibitors from Solanaceae. Wild Solanum species represents repository of protease inhibitor (PIs) diversity and their co-evolutionary trends with the insect proteases ensure its dynamic role. Solanum aculeatissimum Jacq. is commonly known as the African nightshade or Dutch egg plant and is used by local vendors for curing many diseases including viral. In this juncture, the present work targets PIs from S. aculeatissimum in terms of isolation, purification and characterization including kinetics.
Material and methods
Results and discussion
Conclusion Thus, the present work unveils the PI from the fruits of S. aculeatissimum which inhibits trypsin and chymotrypsin in a molar ratio 1:1. SAPI exhibit remarkable stability at temperature and wide range of pH. CD spectral analysis revealed the presence of secondary structure and random coils. Chemical modification studies indicated that lysine and tryptophan in the reactive site of PI which play key role in the protease inhibition mechanism. Future studies are warranted in this direction to completely elucidate the molecular and structural characteristic features of PI from S. aculeatissimum.