To obtain a κ-carrageenase having decomposition activity against κcarrageenan.

This κ-carrageenase is mainly an enzyme catalysing a reaction decomposing κ-carrageenan into neocarrabiose (disaccharide) and neocarratetraose (tetrasaccharide) and has the following physicochemical properties: (a) molecular weight: 35,000; (b) isoelectric point: 9.2; (c) solubility: soluble in water; (d) action: specifically acting on κ-carrageenan as a polysaccharide containing carrabiose which is a disaccharide obtained by binding 3,6-anhydro-D- galactose and D-galactose through α-1,3-bond as a basic structure, polymerizing the carrabiose through β-1,4-bond and further subjecting sulfate group to ester bonding to hydroxyl group at C-4 position of the D-galactose residue, and not acting on neocarrabiose, p-nitrophenol-β-galactophranoside, agar and porphyran; (e) optimum temperature: 40°C; (f) optimum pH: 8.0; (g): pH stability: pH 3.0-11.0; (h) heat stability: stable up to 40°C.