A κ-Carrageenase from a Newly Isolated Pseudoalteromonas-like Bacterium, WZUC10

A bacterial strain able to produce kappa-carrageenase, designated WZUC10, was isolated from a live specimen of the red alga Plocamium telfairiae collected in the East China Sea. The phylogenetic evidence and phenotypic features indicate that this strain belongs to the genus Pseudoalteromonas. WZUC10 requires NaCl for growth and kappa-carrageenan to induce kappa-carrageenase synthesis; galactose and lactose do not induce it. The optimal growth temperature is 23 similar to 270 degrees C. The secreted enzyme, which has a molecular mass of 45 kDa, breaks down kappa-carrageenan into kappa-neocarratetraose sulfate and larger oligosaccharides with a repeating beta-D-Galp4S-(1 -> 4)-alpha-D-AnGalp structure, but cannot degrade kappa-neocarratetraose sulfate or kappa-neocarrahexaose sulfate into kappa-neocarrabiose sulfate. The enzyme retains 90% of its activity after 2 h at 40 degrees C and is completely inactivated after 7.5 min at 70 degrees C, The enzyme's optimal temperature is 30 degrees C and its optimal pH is 7.5. The enzyme-catalyzed reaction follows Michaelis-Menten kinetics, with the Michaelis constant (K-m) and the turnover number (k) being 0.015 mM and 125 s(-1), respectively. WZUC10 produces 50 U/mL kappa-carrageenase after cultivation at 25 degrees C for 35 h on a medium containing 80 g/L glucose, 5 g/L corn steep liquor, 3 g/L kappa-carrageenan, and 15 g/L NaCl. kappa-Neocarratetraose sulfate was prepared simply with precipitation by ethanol:water (5:1, v/v). (C) KSBB