Ao Zihua, Quezada-Calvillo Roberto, Sim Lyann, Nichols Buford L, Rose David R, Sterchi Erwin E, Hamaker Bruce R
Whistler Center for Carbohydrate Research and Department of Food Science, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907-2009, USA.
FEBS Lett. 2007 May 29;581(13):2381-8. doi: 10.1016/j.febslet.2007.04.035. Epub 2007 Apr 24.
Action of human small intestinal brush border carbohydrate digesting enzymes is thought to involve only final hydrolysis reactions of oligosaccharides to monosaccharides. In vitro starch digestibility assays use fungal amyloglucosidase to provide this function. In this study, recombinant N-terminal subunit enzyme of human small intestinal maltase-glucoamylase (rhMGAM-N) was used to explore digestion of native starches from different botanical sources. The susceptibilities to enzyme hydrolysis varied among the starches. The rate and extent of hydrolysis of amylomaize-5 and amylomaize-7 into glucose were greater than for other starches. Such was not observed with fungal amyloglucosidase or pancreatic alpha-amylase. The degradation of native starch granules showed a surface furrowed pattern in random, radial, or tree-like arrangements that differed substantially from the erosion patterns of amyloglucosidase or alpha-amylase. The evidence of raw starch granule degradation with rhMGAM-N indicates that pancreatic alpha-amylase hydrolysis is not a requirement for native starch digestion in the human small intestine.
人类小肠刷状缘碳水化合物消化酶的作用被认为仅涉及寡糖到单糖的最终水解反应。体外淀粉消化率测定使用真菌淀粉酶来提供此功能。在本研究中，人类小肠麦芽糖酶-葡糖淀粉酶的重组N端亚基酶（rhMGAM-N）被用于探索不同植物来源的天然淀粉的消化情况。淀粉对酶水解的敏感性各不相同。蜡质玉米淀粉-5和蜡质玉米淀粉-7水解为葡萄糖的速率和程度高于其他淀粉。真菌淀粉酶或胰腺α-淀粉酶未观察到这种情况。天然淀粉颗粒的降解呈现出随机、放射状或树状排列的表面沟纹模式，这与淀粉酶或α-淀粉酶的侵蚀模式有很大不同。rhMGAM-N对生淀粉颗粒降解的证据表明，胰腺α-淀粉酶水解并非人类小肠中天然淀粉消化的必要条件。
