Characterization of β-N-Acetylhexosaminidase from rhizostomous jellyfish, Rhopilema asamushi, Mesogloea

β-N-Acetylhexosaminidase (EC 3.2.1.52) was purified from rhizostomous jellyfish mesogloea and characterized. Using two purification steps, this enzyme was purified up to 27.4-fold with a recovery rate of 46% compared with crude extract. The molecular weight of the enzyme was estimated to be about 136 kDa, composed of subunit molecular weights of 68 kDa. The enzyme activity was inhibited by SH-reagents, indicating that it contains a SH-group in its active site. The enzyme has a high affinity for pNPGlcNAc with Km value of 0.021 mM. The rate of hydrolysis of N-acetylchito-oligosaccharides tended to decrease with increasing degree of polymerization of the substrate. The parameters of kcat were 92.0 s−1 for pNPGlcNAc, 38.2 s−1 for GlcNAc2, 14.0 s−1 for GlcNAc3, 4.1 s−1 for GlcNAc4, 1.6 s−1 for GlcNAc5, 0.9 s−1 for GlcNAc6, respectively. These results suggest that this β-N-acetylhexosaminidase is an exo-fashion hydrolytic enzyme involved in chitin degradation.