title: Ginger rhizome as a potential source of milk coagulating cysteine protease.
abstract: A milk coagulating protease was purified ∼10.2-fold to apparent homogeneity from ginger rhizomes in 34.9% recovery using ammonium sulfate fractionation, together with ion exchange and size exclusion chromatographic techniques. The molecular mass of the purified protease was estimated to be ∼36kDa by SDS-PAGE, and exhibited a pI of 4.3. It is a glycoprotein with 3% carbohydrate content. The purified enzyme showed maximum activity at pH 5.5 and at a temperature of ∼60°C. Its protease activity was strongly inhibited by iodoacetamide, E-64, PCMB, Hg(2+) and Cu(2+). Inhibition studies and N-terminal sequence classified the enzyme as a member of the cysteine proteases. The cleavage capability of the isolated enzyme was higher for α(s)-casein followed by β- and κ-casein. The purified enzyme differed in molecular mass, pI, carbohydrate content, and N-terminal sequence from previously reported ginger proteases. These results indicate that the purified protease may have potential application as a rennet substitute in the dairy industry.
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Malik Muhammad
authors.initials: MM
authors.lastname: Hashim
authors.forename: Dong
authors.initials: D
authors.lastname: Mingsheng
authors.forename: Muhammad Farooq
authors.initials: MF
authors.lastname: Iqbal
authors.forename: Chen
authors.initials: C
authors.lastname: Xiaohong
mesh_terms: D000818:Animals; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D020939:Zingiber officinale / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D027343:Rhizome / Q000201:enzymology*; D013696:Temperature
chemical_list: D003546:Cysteine Endopeptidases