Cellulose biosynthesis and function in bacteria
Cellulose biosynthesis and function in bacteria
复制标题
DOI：
10.1128/mr.55.1.35-58.1991
复制
发表时间：
1991-03
期刊：
影响因子：
--
通讯作者：
P. Ross;R. Mayer;M. Benziman
中科院分区：
文献类型：
--
作者：
P. Ross;R. Mayer;M. Benziman
目前植物以及细菌中纤维素生物发生的模型认为，膜纤维素合酶复合物将葡萄糖部分从UDP-Glc聚合成β-1，4-葡聚糖链，其在细胞外表面挤出时产生刚性结晶原纤维。除了纤维素原纤维沉积的模式和宽度之外，聚合酶单元的独特排列和缔合程度大概还控制着细胞外链的组装。最明显的是，对于木醋杆菌，聚合和组装似乎是紧密耦合的。迄今为止，只有细菌在生物化学和遗传水平上得到了有效的研究。以.木纤维素合成酶由至少两个结构相似但功能不同的亚基组成，受到多组分调节系统的控制。调节是基于新的核苷酸环二鸟苷酸，一种正变构效应物，和维持其细胞内周转的调节酶：二鸟苷酸环化酶和Ca 2（+）-敏感的双-（3 '，5'）-环二鸟苷酸（c-di-GMP）磷酸二酯酶。从A.木质素，其构成用于纤维素合成的操纵子。第二个基因编码纤维素合成酶的催化亚基;其他三个基因产物的功能仍然未知。细菌纤维素作为一种胞外产物，在自然界中发挥着多种生物学作用，对A.或在根瘤菌属和土壤杆菌属物种中的共生或感染相互作用期间促进细胞粘附。A.木质纤维素被证明是最适合工业用途的，允许细菌纤维素的独特特性被开发用于新的产品应用。
The current model of cellulose biogenesis in plants, as well as bacteria, holds that the membranous cellulose synthase complex polymerizes glucose moieties from UDP-Glc into beta-1,4-glucan chains which give rise to rigid crystalline fibrils upon extrusion at the outer surface of the cell. The distinct arrangement and degree of association of the polymerizing enzyme units presumably govern extracellular chain assembly in addition to the pattern and width of cellulose fibril deposition. Most evident for Acetobacter xylinum, polymerization and assembly appear to be tightly coupled. To date, only bacteria have been effectively studied at the biochemical and genetic levels. In A. xylinum, the cellulose synthase, composed of at least two structurally similar but functionally distinct subunits, is subject to a multicomponent regulatory system. Regulation is based on the novel nucleotide cyclic diguanylic acid, a positive allosteric effector, and the regulatory enzymes maintaining its intracellular turnover: diguanylate cyclase and Ca2(+)-sensitive bis-(3',5')-cyclic diguanylic acid (c-di-GMP) phosphodiesterase. Four genes have been isolated from A. xylinum which constitute the operon for cellulose synthesis. The second gene encodes the catalytic subunit of cellulose synthase; the functions of the other three gene products are still unknown. Exclusively an extracellular product, bacterial cellulose appears to fulfill diverse biological roles within the natural habitat, conferring mechanical, chemical, and physiological protection in A. xylinum and Sarcina ventriculi or facilitating cell adhesion during symbiotic or infectious interactions in Rhizobium and Agrobacterium species. A. xylinum is proving to be most amenable for industrial purposes, allowing the unique features of bacterial cellulose to be exploited for novel product applications.