Taylor Larry E, Henrissat Bernard, Coutinho Pedro M, Ekborg Nathan A, Hutcheson Steven W, Weiner Ronald M
Department of Marine and Estuarine Environmental Sciences, University of Maryland, College Park, MD 20742, USA.
J Bacteriol. 2006 Jun;188(11):3849-61. doi: 10.1128/JB.01348-05.
Saccharophagus degradans strain 2-40 is a representative of an emerging group of marine complex polysaccharide (CP)-degrading bacteria. It is unique in its metabolic versatility, being able to degrade at least 10 distinct CPs from diverse algal, plant and invertebrate sources. The S. degradans genome has been sequenced to completion, and more than 180 open reading frames have been identified that encode carbohydrases. Over half of these are likely to act on plant cell wall polymers. In fact, there appears to be a full array of enzymes that degrade and metabolize plant cell walls. Genomic and proteomic analyses reveal 13 cellulose depolymerases complemented by seven accessory enzymes, including two cellodextrinases, three cellobiases, a cellodextrin phosphorylase, and a cellobiose phosphorylase. Most of these enzymes exhibit modular architecture, and some contain novel combinations of catalytic and/or substrate binding modules. This is exemplified by endoglucanase Cel5A, which has three internal family 6 carbohydrate binding modules (CBM6) and two catalytic modules from family five of glycosyl hydrolases (GH5) and by Cel6A, a nonreducing-end cellobiohydrolase from family GH6 with tandem CBM2s. This is the first report of a complete and functional cellulase system in a marine bacterium with a sequenced genome.
食糖嗜纤维菌2-40菌株是一类新兴的海洋复合多糖（CP）降解细菌的代表。它在代谢多样性方面独具特色，能够降解至少10种来自不同藻类、植物和无脊椎动物来源的不同CP。食糖嗜纤维菌的基因组已测序完成，已鉴定出180多个编码碳水化合物酶的开放阅读框。其中一半以上可能作用于植物细胞壁聚合物。事实上，似乎存在一整套降解和代谢植物细胞壁的酶。基因组和蛋白质组分析揭示了13种纤维素解聚酶，并辅以7种辅助酶，包括两种纤维糊精酶、三种纤维二糖酶、一种纤维糊精磷酸化酶和一种纤维二糖磷酸化酶。这些酶大多呈现模块化结构，有些包含催化和/或底物结合模块的新颖组合。以内切葡聚糖酶Cel5A为例，它有三个内部6家族碳水化合物结合模块（CBM6）和两个来自糖基水解酶5家族（GH5）的催化模块；还有Cel6A，一种来自GH6家族的非还原端纤维二糖水解酶，带有串联的CBM2s。这是在具有已测序基因组的海洋细菌中首次报道完整且功能齐全的纤维素酶系统。
