Laboratory of Protein Evolution, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, SK-84551 Bratislava, Slovakia.
Enzyme Microb Technol. 2011 Oct 10;49(5):429-40. doi: 10.1016/j.enzmictec.2011.07.002. Epub 2011 Jul 18.
Starch-binding domains (SBDs) comprise distinct protein modules that bind starch, glycogen or related carbohydrates and have been classified into different families of carbohydrate-binding modules (CBMs). The present review focuses on SBDs of CBM20 and CBM48 found in amylolytic enzymes from several glycoside hydrolase (GH) families GH13, GH14, GH15, GH31, GH57 and GH77, as well as in a number of regulatory enzymes, e.g., phosphoglucan, water dikinase-3, genethonin-1, laforin, starch-excess protein-4, the β-subunit of AMP-activated protein kinase and its homologues from sucrose non-fermenting-1 protein kinase SNF1 complex, and an adaptor-regulator related to the SNF1/AMPK family, AKINβγ. CBM20s and CBM48s of amylolytic enzymes occur predominantly in the microbial world, whereas the non-amylolytic proteins containing these modules are mostly of plant and animal origin. Comparison of amino acid sequences and tertiary structures of CBM20 and CBM48 reveals the close relatedness of these SBDs and, in some cases, glycogen-binding domains (GBDs). The families CBM20 and CBM48 share both an ancestral form and the mode of starch/glycogen binding at one or two binding sites. Phylogenetic analyses demonstrate that they exhibit independent behaviour, i.e. each family forms its own part in an evolutionary tree, with enzyme specificity (protein function) being well represented within each family. The distinction between CBM20 and CBM48 families is not sharp since there are representatives in both CBM families that possess an intermediate character. These are, for example, CBM20s from hypothetical GH57 amylopullulanase (probably lacking the starch-binding site 2) and CBM48s from the GH13 pullulanase subfamily (probably lacking the starch/glycogen-binding site 1). The knowledge gained concerning the occurrence of these SBDs and GBDs through the range of taxonomy will support future experimental research.
淀粉结合域（SBDs）由结合淀粉、糖原或相关碳水化合物的独特蛋白质模块组成，并已被分类为不同的碳水化合物结合模块（CBMs）家族。本综述重点介绍了几种类糖苷水解酶（GH）家族 GH13、GH14、GH15、GH31、GH57 和 GH77 中的淀粉酶以及一些调节酶中的 CBM20 和 CBM48，例如磷酸葡聚糖、水二激酶-3、genethonin-1、laforin、淀粉过量蛋白-4、AMP 激活蛋白激酶的β亚基及其来自蔗糖非发酵-1 蛋白激酶 SNF1 复合物的同源物，以及与 SNF1/AMPK 家族相关的衔接调节因子 AKINβγ。淀粉酶中的 CBM20 和 CBM48 主要存在于微生物世界中，而含有这些模块的非淀粉酶蛋白主要来自植物和动物。CBM20 和 CBM48 的氨基酸序列和三级结构比较揭示了这些 SBDs 的密切相关性，在某些情况下，还揭示了糖原结合域（GBDs）的密切相关性。CBM20 和 CBM48 家族都具有祖先形式和在一个或两个结合位点结合淀粉/糖原的模式。系统发育分析表明，它们表现出独立的行为，即每个家族都在进化树中形成自己的部分，并且每个家族都很好地代表了酶的特异性（蛋白质功能）。CBM20 和 CBM48 家族之间的区别并不明显，因为在两个 CBM 家族中都有代表具有中间特征的成员。例如，来自假设的 GH57 淀粉 pullulanase 的 CBM20（可能缺乏淀粉结合位点 2）和来自 GH13 pullulanase 亚家族的 CBM48（可能缺乏淀粉/糖原结合位点 1）。通过分类学范围获得的关于这些 SBD 和 GBD 存在的知识将支持未来的实验研究。
