Purification and Characterization of a κ-carrageenase from Marine Pseudoalteromonas sp.QY202

A marine bacterium Pseudoalteromonas sp.QY202 with high κ-carrageenase activity was isolated from the surface of Chondrus crispus.The κ-carrageenase was purified to electrophoretic homogeneity from the culture supernatant by a procedure of ammonium sulfate precipitation,desalting and DEAE-sepharose ion exchange chromatography,and the characterization of the enzyme was studied.The results show that the enzyme is purified 23.1 folds with a total recovery yield of 43.9% and gives a single band on SDS-PAGE with a molecular mass of 33.2 kDa.The optimum temperature and pH for enzyme activity are 40 ℃ and pH8.0,respectively.The enzyme is stable at temperatures below 40 ℃ and over a range of pH7.0-8.0.For κ-carrageenan,the enzyme gave a Km value of 1.6 mg/mL.The enzyme activity could be enhanced by the presence of Na＋ and K＋,whereas enormously inhibited by Hg^2＋and Cu^2＋.The main hydrolysis products of κ-carrageenan by the enzyme are κ-neocarradiaose and κ-neocarratetraose.