Choi Ji-Hye, Lee Heeseob, Kim Young-Wan, Park Jong-Tae, Woo Eui-Jeon, Kim Myo-Jeong, Lee Byong-Hoon, Park Kwan-Hwa
Center for Agricultural Biomaterials and Department of Food Science and Biotechnology, Seoul National University, Seoul 151-921, Republic of Korea.
Biochem Biophys Res Commun. 2009 Jan 9;378(2):224-9. doi: 10.1016/j.bbrc.2008.11.020. Epub 2008 Nov 14.
A novel debranching enzyme from Nostoc punctiforme PCC73102 (NPDE) exhibits hydrolysis activity toward both alpha-(1,6)- and alpha-(1,4)-glucosidic linkages. The action patterns of NPDE revealed that branched chains are released first, and the resulting maltooligosaccharides are then hydrolyzed. Analysis of the reaction with maltooligosaccharide substrates labeled with (14)C-glucose at the reducing end shows that NPDE specifically liberates glucose from the reducing end. Kinetic analyses showed that the hydrolytic activity of NPDE is greatly affected by the length of the substrate. The catalytic efficiency of NPDE increased considerably upon using substrates that can occupy at least eight glycone subsites such as maltononaose and maltooctaosyl-alpha-(1,6)-beta-cyclodextrin. These results imply that NPDE has a unique subsite structure consisting of -8 to +1 subsites. Given its unique subsite structure, side chains shorter than maltooctaose in amylopectin were resistant to hydrolysis by NPDE, and the population of longer side chains was reduced.
来自点状念珠藻PCC73102的一种新型脱支酶（NPDE）对α-(1,6)-和α-(1,4)-糖苷键均表现出水解活性。NPDE的作用模式表明，支链首先被释放，然后生成的麦芽寡糖被水解。对用还原端标记有(14)C-葡萄糖的麦芽寡糖底物的反应分析表明，NPDE从还原端特异性释放葡萄糖。动力学分析表明，NPDE的水解活性受底物长度的影响很大。当使用可占据至少八个糖基亚位点的底物（如麦芽九糖和麦芽八糖基-α-(1,6)-β-环糊精）时，NPDE的催化效率显著提高。这些结果表明，NPDE具有由-8至+1亚位点组成的独特亚位点结构。鉴于其独特的亚位点结构，支链淀粉中短于麦芽八糖的侧链对NPDE的水解具有抗性，且较长侧链的比例降低。
