Biotechnology Program, Biochemistry Department, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
BMB Rep. 2011 Jun;44(6):375-80. doi: 10.5483/BMBRep.2011.44.6.375.
Bacillus licheniformis SK-1 naturally produces chitinase 72 (CHI72) with two truncation derivatives at the C-terminus, one with deletion of the chitin binding domain (ChBD), and the other with deletions of both fibronectin type III domain (FnIIID) and ChBD. We constructed deletions mutants of CHI72 with deletion of ChBD (CHI72ΔChBD) and deletions of both FnIIID and ChBD (CHI72ΔFnIIIDΔChBD), and studied their activity on soluble, amorphous and crystalline substrates. Interestingly, when equivalent amount of specific activity of each enzyme on soluble substrate was used, the product yield from CHI72- ΔChBD and CHI72ΔFnIIIDΔChBD on colloidal chitin was 2.5 and 1.6 fold higher than CHI72, respectively. In contrast, the product yield from CHI72ΔChBD and CHI72ΔFnIIID- ΔChBD on Β-chitin reduced to 0.7 and 0.5 fold of CHI72, respectively. These results suggest that CHI72 can modulate its substrate specificities through truncations of the functional domains at the C-terminus, producing a mixture of enzymes with elevated efficiency of hydrolysis.
地衣芽孢杆菌 SK-1 天然产生的几丁质酶 72（CHI72）在 C 末端有两个截短衍生物，一个缺失了几丁质结合域（ChBD），另一个缺失了纤维连接蛋白 III 结构域（FnIIID）和 ChBD。我们构建了 CHI72 的缺失突变体，缺失了 ChBD（CHI72ΔChBD）和 FnIIID 和 ChBD（CHI72ΔFnIIIDΔChBD），并研究了它们在可溶性、无定形和结晶底物上的活性。有趣的是，当使用每种酶在可溶性底物上的等效比活度时，CHI72-ΔChBD 和 CHI72ΔFnIIIDΔChBD 在胶体几丁质上的产物产率分别比 CHI72 高 2.5 和 1.6 倍。相比之下，CHI72ΔChBD 和 CHI72ΔFnIIIDΔChBD 在 Β-几丁质上的产物产率分别降至 CHI72 的 0.7 和 0.5 倍。这些结果表明，CHI72 可以通过 C 末端功能域的截断来调节其底物特异性，产生一种水解效率提高的酶混合物。
