Macromolecular Crystallography Unit, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, EAN, 2780-157, Oeiras, Protugal.
J Biol Inorg Chem. 2014 Jun;19(4-5):505-13. doi: 10.1007/s00775-014-1105-x. Epub 2014 Feb 19.
Arabinanase is a glycosyl hydrolase that is able to cleave the glycosidic bonds of α-1,5-L-arabinan, releasing arabino-oligosaccharides and L-arabinose. The enzyme has two domains, an N-terminal catalytic domain with a characteristic β-propeller fold and a C-terminal domain whose function is unknown. A calcium ion, located near the catalytic site, serves to stabilize the N-terminal domain, but it has also been proposed to play a key role in the enzyme mechanism. The present work describes the structure of an inactive mutant of the wild-type enzyme (H318Q) and in which the calcium ion has been adventitiously replaced by nickel. These structural studies, together with functional and modelling studies, clearly support the role of the calcium ion in the overall reaction mechanism.
阿拉伯聚糖酶是一种糖苷水解酶，能够切割α-1,5-L-阿拉伯聚糖的糖苷键，释放阿拉伯寡糖和 L-阿拉伯糖。该酶有两个结构域，一个 N 端催化结构域具有特征性的β-桨叶折叠，另一个 C 端结构域的功能未知。一个位于催化部位附近的钙离子，用于稳定 N 端结构域，但也有人提出它在酶机制中起着关键作用。本工作描述了野生型酶（H318Q）的一种无活性突变体的结构，其中钙离子被意外地被镍取代。这些结构研究，以及功能和建模研究，清楚地支持钙离子在整个反应机制中的作用。
