以猪小肠黏膜提取物作为α-葡萄糖苷酶和二肽基肽酶IV的酶活力分析体系的建立

α-葡萄糖苷酶和二肽基肽酶IV（dipeptidyl peptidase 4，DPP-4）是II型糖尿病治疗中2 种重要的靶向酶。这两种商品化酶价格昂贵且主要来源于微生物，难以有效用于两种酶抑制剂的筛选，而这两种酶均普遍存在哺乳动物的小肠中。为了获得经济有效、来源于哺乳动物体内的α-葡萄糖苷酶和DPP-4，本研究收集新鲜的猪小肠黏膜分泌物及上皮细胞，对比分析了猪小肠不同部位黏膜提取物的α-葡萄糖苷酶和DPP-4的活力。以猪小肠黏膜提取物作为α-葡萄糖苷酶和DPP-4的酶反应体系，并且利用这两种酶的阳性药（阿卡波糖和抑二肽素A（diprotin A，IPI））分别进行了抑制率验证和评价。阿卡波糖对商品和猪回肠源α-葡萄糖苷酶的半数有效抑制质量浓度（median inhibition concentration，IC50）分别是1.102 4、0.244 7 mg/mL；IPI对商品和猪回肠源DPP-4的IC50分别为19.119 7、41.268 4 μg/mL。通过比较发现，猪回肠黏膜提取物的α-葡萄糖苷酶和DPP-4比活力分别为0.084 1、0.053 4 U/mg，在3 种黏膜提取物中均为最高，因此选择猪回肠黏膜提取物作为商品化α-葡萄糖苷酶和DPP-4的替代物进行抑制剂的筛选。

Establishment of Activity Assays for α-Glucosidase and Dipeptidyl Peptidase IV Using Porcine Small Intestine Mucosal Extracts

Alpha-glucosidase and dipeptidyl peptidase IV (DPP-4) are two important target enzymes useful in the treatment of type II diabetes. Currently, commercially available enzymes are mainly obtained from microorganisms, making it difficult to screen for inhibitors of the enzymes. Both enzymes are widespread in mammalian small intestines. In this study, fresh porcine small intestinal mucosal secretions and epithelial cells were collected for comparative measurement of α-glucosidase and DPP-4 activities in mucosal extracts from three different intestinal segments. The extracts were used as reaction system of α-glucosidase and DPP-4 and their percentage inhibition by acarbose and diprotin A (IPI) respectively was evaluated. The median inhibition concentration (IC50) against commercial and porcine ileum-derived α-glucosidase was 1.102 4 and 0.244 7 mg/mL for acarbose, and 19.119 7 and 41.268 4 μg/mL for IPI, respectively. The specific activities of α-glucosidase and DPP-4 in porcine ileum mucosal extract were 0.084 1 and 0.053 4 U/mg, which were higher than those in the two other mucosal extracts. Therefore, porcine ileum mucosal extract can be used as an alternative to commercial α-glucosidase and DPP-4 for screening for enzyme inhibitors.