title: Purification and characterization of milk clotting enzyme from goat (Capra hircus).
abstract: Chymosin, the major component of rennet (milk clotting enzyme), is an acid protease produced in the fourth stomach of milk-fed ruminants including goat and sheep in the form of an inactive precursor prochymosin. It is responsible for hydrolysis of kappa-casein chain in casein micelles of milk and therefore, used as milk coagulant in cheese preparation. The present investigation was undertaken to purify and characterize goat (Capra hircus) chymosin for its suitability as milk coagulant. The enzyme was extracted from abomasal tissue of kid and purified nearly 30-fold using anion exchanger and gel filtration chromatography. Goat chymosin resolved into three major active peaks, indicating possible heterogeneity when passed through DEAE-cellulose ion exchange column. The purified enzyme had a molecular mass of 36 kDa on SDS-PAGE, which was further confirmed by Western blot analysis. The purified enzyme preparation was stable up to 55 degrees C with maximum activity at 30 degrees C. The milk clotting activity was decreased steadily as pH is increased and indicated maximum activity at pH 5.5. Proteolytic activity of goat chymosin increased with incubation time at 37 degrees C. Goat chymosin was found to be more thermostable than cattle chymosin and equally stable to buffalo chymosin.
authors.affiliation: Division of Dairy Microbiology, National Dairy Research Institute, Karnal-132 001, India. ashwanindri@rediffmail.com <ashwanindri@rediffmail.com>
authors.forename: Ashwani
authors.initials: A
authors.lastname: Kumar
authors.forename: Jitender
authors.initials: J
authors.lastname: Sharma
authors.forename: Ashok Kumar
authors.initials: AK
authors.lastname: Mohanty
authors.forename: Sunita
authors.initials: S
authors.lastname: Grover
authors.forename: Virender Kumar
authors.initials: VK
authors.lastname: Batish
mesh_terms: D000018:Abomasum / Q000201:enzymology; D000818:Animals; D002852:Chromatography, Ion Exchange; D012085:Chymosin / Q000737:chemistry / Q000302:isolation & purification*; D006041:Goats / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000201:enzymology*; D013696:Temperature
chemical_list: D012085:Chymosin