Glucan branching enzymes (GBEs, EC 2.4.1.18) catalyze the formation of α-1,6-linked branch in starch, which is important for the starch modification with prospective properties. In this study, the aqGBE gene encoding an efficient glucan branching enzyme was cloned from Aquabacterium sp. strain A7-Y and successfully expressed in Escherichia coli BL21 (DE3). The specific activity of the purified recombinant enzyme rAqGBE was 2850 U/mg with potato starch as the optimal substrate, and the K_m and V_max values of rAqGBE were 1.18 mg/mL and 588.2 μmol/min/mg, respectively. Enzymological characterization showed that rAqGBE exhibits its optimal activity under the condition of 40 °C and pH 7.0, respectively, which is independent of calcium ions. Otherwise, rAqGBE-treated potato starch showed different chain length distribution compared with control, the numbers of short chains (degree of polymerization, DP < 7) and long chains (DP > 25) increased from 4.5% to 9.6% and 6.1%–15.7% after enzymatic treatment, respectively. In starch anti-ageing assay, with minimum usage of 0.8 mg rAqGBE per g starch, the rAqGBE-treated potato starch exhibited reduced retrogradation properties. Our results indicate that the branching enzyme AqGBE may therefore be a promising tool for the enzymatic modification of starch.

葡聚糖支化酶（GBEs，EC 2.4.1.18）催化淀粉中与α-1,6-相连的分支的形成，这对具有预期特性的淀粉修饰非常重要。在这项研究中，从Aquabacterium sp。克隆了编码高效葡聚糖分支酶的aqGBE基因。菌株A7-Y，并在大肠杆菌BL21（DE3）中成功表达。以马铃薯淀粉为最佳底物，纯化的重组酶rAqGBE的比活为2850 U / mg，K _m和V _maxrAqGBE的值分别为1.18 mg / mL和588.2μmol/ min / mg。酶学表征表明，rAqGBE分别在40°C和pH 7.0的条件下表现出最佳活性，而与钙离子无关。否则，rAqGBE处理的马铃薯淀粉与对照相比显示出不同的链长分布，短链（聚合度，DP <7）和长链（DP> 25）的数量从4.5％增加到9.6％和6.1％–15.7分别用酶处理后的％。在淀粉抗老化试验中，每克淀粉的最低用量为0.8 mg rAqGBE，经rAqGBE处理的马铃薯淀粉的回生特性降低。我们的结果表明，支化酶AqGBE可能是淀粉酶促修饰的有前途的工具。