Mathieu Sophie, Henrissat Bernard, Labre Flavien, Skjåk-Bræk Gudmund, Helbert William
CERMAV, CNRS and Grenoble Alpes Université, BP53, 38000, Grenoble, Cedex 9, France.
Centre National de la Recherche Scientifique (CNRS), UMR7257, Université Aix-Marseille, 13288, Marseille, France.
PLoS One. 2016 Jul 20;11(7):e0159415. doi: 10.1371/journal.pone.0159415. eCollection 2016.
Alginate, the main cell-wall polysaccharide of brown algae, is composed of two residues: mannuronic acid (M-residues) and, its C5-epimer, guluronic acid (G-residues). Alginate lyases define a class of enzymes that cleave the glycosidic bond of alginate by β-elimination. They are classified according to their ability to recognize the distribution of M- and G-residues and are named M-, G- or MG-lyases. In the CAZy database, alginate lyases have been grouped by sequence similarity into seven distinct polysaccharide lyase families. The polysaccharide lyase family PL6 is subdivided into three subfamilies. Subfamily PL6_1 includes three biochemically characterized enzymes (two alginate lyases and one dermatan sulfatase lyase). No characterized enzymes have been described in the two other subfamilies (PL6_2 and PL6_3). To improve the prediction of polysaccharide-lyase activity in the PL6 family, we re-examined the classification of the PL6 family and biochemically characterized a set of enzymes reflecting the diversity of the protein sequences. Our results show that subfamily PL6_1 includes two dermatan sulfates lyases and several alginate lyases that have various substrate specificities and modes of action. In contrast, subfamilies PL6_2 and PL6_3 were found to contain only endo-poly-MG-lyases.
褐藻的主要细胞壁多糖——藻酸盐，由两种残基组成：甘露糖醛酸（M-残基）及其C5-差向异构体古洛糖醛酸（G-残基）。藻酸盐裂解酶是一类通过β-消除作用切割藻酸盐糖苷键的酶。它们根据识别M-和G-残基分布的能力进行分类，分别命名为M-、G-或MG-裂解酶。在CAZy数据库中，藻酸盐裂解酶已根据序列相似性被归为七个不同的多糖裂解酶家族。多糖裂解酶家族PL6又细分为三个亚家族。亚家族PL6_1包含三种已进行生化特征鉴定的酶（两种藻酸盐裂解酶和一种硫酸皮肤素裂解酶）。另外两个亚家族（PL6_2和PL6_3）中尚未描述有特征明确的酶。为了改进对PL6家族多糖裂解酶活性的预测，我们重新审视了PL6家族的分类，并对一组反映蛋白质序列多样性的酶进行了生化特征鉴定。我们的结果表明，亚家族PL6_1包含两种硫酸皮肤素裂解酶和几种具有不同底物特异性和作用模式的藻酸盐裂解酶。相比之下，发现亚家族PL6_2和PL6_3仅包含内切聚MG-裂解酶。
