Religiosin C, a cucumisin-like serine protease from Ficus religiosa

A serine protease was purified to homogeneity from the latex of Ficus religiosa. The enzyme, named religiosin C is a monomer with molecular mass of 80 kDa. The enzymatic activity of the protein was inhibited by serine protease inhibitors. Isoelectric point of the enzyme is pH 4.6 with optimum pH and temperature of pH 6–8 and 45–50 °C, respectively. The specific extinction coefficient (ε2801%) of the enzyme is 14.68 with 16 tryptophan, 20 tyrosine and 7 cysteine residues in its molecular structure. The enzyme shows broad substrate specificity and hydrolyzes both natural and synthetic substrates. The enzyme is highly stable over a broad range of pH and temperature as well as in the presence of high concentration of chemical denaturants, organic solvents and metal ions. The N-terminal residues of religiosin C exhibited considerable homology with cucumisin and other cucumisin/subtilisin-like serine proteases. The high milk-clotting ability of religiosin C supports its probable use in the food and other biotechnological industries.

► Religiosin C is novel milk-clotting serine protease from a vegetal source. ► Enzyme is active over a wide range of pH and temperature. ► Enzyme is highly stable against denaturants, organic solvents and metal ions. ► Enzyme exhibits high milk-clotting activity in alkaline medium. ► Enzyme is quite resistant to autodigestion at higher concentration.