Partial Characterization of an Enzymatic Extract from Bentong Ginger (Zingiber officinale var. Bentong)

Extraction of protease from a local ginger rhizome (Zingiber officinale var. Bentong) was carried out. The effect of extraction pH (6.4, 6.8, 7.0, 7.2, 7.6, 8.0, 8.4, and 8.8) and stabilizers (0.2% ascorbic acid, 0.2% ascorbic acid and 5 mM EDTA, or 10 mM cysteine and 5 mM EDTA) on protease activity during extraction was examined. pH 7.0 potassium phosphate buffer and 10 mM cysteine in combination with 5 mM EDTA as stabilizer were found to be the most effective conditions. The extraction procedure yielded 0.73% of Bentong ginger protease (BGP) with a specific activity of 24.8 ± 0.2 U/mg protein. Inhibitory tests with some protease inhibitors classified the enzyme as a cysteine protease. The protease showed optimum activity at 60 °C and pH 6–8, respectively. The enzyme was completely inhibited by heavy metal cations such as Cu²⁺, and Hg²⁺. SDS stimulated the activity of enzyme, while emulsifiers (Tween 80 and Tween 20) slightly reduced its activity. The kinetic analysis showed that the protease has K_m and V_max values of 0.21 mg mL⁻¹ and 34.48 mg mL⁻¹ min⁻¹, respectively. The dried enzyme retained its activity for 22 months when stored at −20 °C.