title: Purification and characterization of extracellular inulinase from a marine yeast Cryptococcus aureus G7a and inulin hydrolysis by the purified inulinase.
abstract: The extracellular inulinase in the supernatant of the cell culture of the marine yeast Cryptococcus aureus G7a was purified to homogeneity with a 7.2-fold increase in specific inulinase activity compared to that in the supernatant by ultrafiltration, concentration, gel filtration chromatography (Sephadex G-75), and anion exchange chromatography (DEAE sepharose fast flow anion exchange). The molecular mass of the purified enzyme was estimated to be 60.0 kDa. The optimal pH and temperature of the purified enzyme were 5.0 and 50 degrees C, respectively. The enzyme was activated by Ca2+, K+, Na+, Fe2+, and Zn2+. However, Mg2+, Hg2+, and Ag+ acted as inhibitors in decreasing the activity of the purified inulinase. The enzyme was strongly inhibited by phenylmethanesulphonyl fluoride (PMSF), iodoacetic acid, EDTA, and 1,10-phenanthroline. The K(m) and Vmax values of the purified enzyme for inulin were 20.06 mg/ml and 0.0085 mg/min, respectively. A large amount of monosaccharides were detected after the hydrolysis of inulin with the purified inulinase, indicating the purified inulinase had a high exoinulinase activity.
authors.affiliation: Unesco Chinese Center of Marine Biotechnology, Ocean University of China, Yushan Road, No. 5, Qingdao, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Sheng
authors.forename: Zhenming
authors.initials: Z
authors.lastname: Chi
authors.forename: Fang
authors.initials: F
authors.lastname: Gong
authors.forename: Jing
authors.initials: J
authors.lastname: Li
mesh_terms: D003454:Cryptococcus / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007444:Inulin / Q000737:chemistry*; D012623:Seawater / Q000382:microbiology; D013696:Temperature
chemical_list: D007444:Inulin; D006026:Glycoside Hydrolases; C023086:inulinase