Facile synthesis of insulin fusion derivatives through sortase A ligation

Insulin derivatives such as insulin detemir and insulin degludec are U.S. Food and Drug Administration (FDA)-approved long-acting insulin currently used by millions of people with diabetes. These derivatives are modified in C-terminal B29 lysine to retain insulin bioactivity. New and efficient methods for facile synthesis of insulin derivatives may lead to new discovery of therapeutic insulin. Herein, we report a new method using sortase A (SrtA)-mediated ligation for the synthesis of insulin derivatives with high efficiency and functional group tolerance in the C-terminal B chain. This new insulin molecule (Ins-SA) with an SrtA-recognizing motif can be conjugated to diverse groups with N-terminal oligoglycines to generate new insulin derivatives. We further demonstrated that a new insulin derivative synthesized by this SrtA-mediated ligation shows strong cellular and in vivo bioactivity. This enzymatic method can therefore be used for future insulin design and development.     

Sortase A酶突变体的原核表达、纯化及活性测定（英文）

本研究采用pET28a载体对金黄色葡萄球菌(Staphylococcus aureus)中的转肽酶A(sortase A,SrtA)截短体SrtA?N25以及突变体m5SrtA?N59、m9SrtA?N59进行了原核发酵表达,并通过镍柱亲和色谱、阳离子交换色谱进行蛋白纯化。随后,通过荧光共振能量转移试验比较了3种酶的催化活性,测定了酶反应动力学常数、筛选了最适反应条件,并进一步探究了不同生化试剂对SrtA酶学活性的影响。结果显示,SrtA?N25、m5SrtA?N59、m9SrtA?N59在大肠埃希菌中均能以可溶形式高效表达,且纯化后得到的高纯度SrtA酶均具有生物学活性。相较于SrtA?N25,m5SrtA?N59、m9SrtA?N59活性分别提高了约68、5 544倍,尤其是m9SrtA?N59的催化活性大大提高。m9SrtA?N59的最适反应温度为30~37℃,最适反应pH值为6.0~7.0,反应体系中加入三(2-羧乙基)膦(TCEP)、二硫苏糖醇(DTT)等还原剂有助于增强SrtA酶催化活性。