中国生物工程杂志

The residues of natural polysaccharide substrates were often substituted by acetyl groups, and acetyl esterase can cut acetyl groups on these substrates, which is conducive to the further degradation. The gene aesA which encoding an acetyl esterase was cloned from mannan utilization gene cluster of Bacillus sp. N16-5 and heterologously expressed in prokaryotic host. The gene aesA is 957bp long and encodes 318 amino acids, belonging to the carbohydrate esterase family 7 (CE7). AesA showed good catalytic activity for 4-methylumbelliferyl-acetate and pNP-acetate, however, there was no active effect on alpha-naphthyl acetate. The enzyme activity for 4-methylumbelliferyl-acetate is 1.68U/mg, and the kinetic parameters K_m, V_max and k_cat/K_m, were measured by 3.27mmol/L, 0.044mmol/min and 289.71ms^-1, respectively. Metal ions Fe³⁺, Fe²⁺, Mn²⁺ and Cu²⁺ all promoted the activity of AesA, and Cu²⁺ exhibited the most significant promoting effect. AesA has a significant synergistic effect with β-mannanase ManA on degrading acetylated mannan substrates, and the synergy degree reached 1.47 when using acetylated locust bean gum as substrate. It is helpful to understand the mannan utilization mechanism of Bacillus sp. N16-5, and has potential application prospects in mannan degradation.