Properties of proteolytic enzyme from ginger (Zingiber officinale Roscoe)

Proteases in ginger rhizome have the potentials in industrial applications. This study was \nconducted to extract and characterize the proteolytic enzyme from ginger ( \nZingiber officinale \nRoscoe). Ginger protease (GP) was extracted from ginger rhizome by homogenization with \n100 mM potassium phosphate buffer pH 7.0 containing 10 mM cysteine and 5 mM EDTA \nwhich were found to be the most efficient extraction buffer and stabilizers. After centrifugation \nat 10,500 x g, protein in the crude extract was precipitated using 60% ammonium sulfate \nfollowing which the precipitate was redissolved in 50 mM potassium phosphate buffer pH 7.0, \ndialyzed and then lyophilized. The extraction method yielded 0.94% (w/w of fresh weight) of \nGP with a specific activity of 27.6 ± 0.1 Unit/mg protein where 1 Unit is defined as the amount \nof protease causing an increase in absorbance by 1 unit per minute using azocasein as the \nsubstrate. Results show that the GP was completely inhibited by heavy metal cations i.e. Cu \n2+ \nand Hg \n2+ \n, and a thiol blocking agent or inhibitor, n-ethyl maleimide (NEM), indicating that GP \nis most probably a cysteine protease. The enzyme has an optimum temperature at 60 \no \nC and the \noptimum pH ranged between pH 6 to 8. Monovalent cations (K \n+ \nand Na \n+ \n) have no significant \neffect on activity of GP, but divalent and trivalent cations showed moderate inhibitory effect. \nDetergents such as sodium dodecyl sulfate increased the activity of GP while Tween 80 and \nTween 20 slightly reduced the activity. \n \n \n