Paradis F W, Zhu H, Krell P J, Phillips J P, Forsberg C W
Department of Microbiology, University of Guelph, Ontario, Canada.
J Bacteriol. 1993 Dec;175(23):7666-72. doi: 10.1128/jb.175.23.7666-7672.1993.
The xynC gene of Fibrobacter succinogenes S85 codes for a 66.4-kDa xylanase which consists of three distinct domains separated by two flexible regions rich in serine residues. Domains A and B of XynC code for catalytic domains with 56.5% identity and 9.6% similarity with each other, and both domains share homology with xylanases of Ruminococcus flavefaciens, Neocallimastix patriciarum, Clostridium acetobutylicum, Bacillus pumilus, Bacillus subtilis, and Bacillus circulans. More than 88% of the xylanase activity of Escherichia coli cells carrying the original 13-kb recombinant plasmid was released from intact cells by cold water washes. The major products of hydrolysis of xylan by both domains were xylose and xylobiose, indicating that the xynC gene product exhibits catalytic properties similar to those of the XynA xylanases from R. flavefaciens and N. patriciarum. So far, these features are not shared broadly with bacteria from other environments and may indicate specific selection for this domain structure in the highly competitive environment of the rumen.
琥珀酸纤维杆菌S85的xynC基因编码一种66.4 kDa的木聚糖酶，该酶由三个不同的结构域组成，这三个结构域被两个富含丝氨酸残基的柔性区域隔开。XynC的结构域A和B编码催化结构域，它们彼此之间的同一性为56.5%，相似性为9.6%，并且这两个结构域与黄化瘤胃球菌、梨形新丽鞭毛虫、丙酮丁醇梭菌、短小芽孢杆菌、枯草芽孢杆菌和环状芽孢杆菌的木聚糖酶具有同源性。携带原始13 kb重组质粒的大肠杆菌细胞中，超过88%的木聚糖酶活性可通过冷水洗涤从完整细胞中释放出来。两个结构域对木聚糖水解的主要产物都是木糖和木二糖，这表明xynC基因产物表现出与黄化瘤胃球菌和梨形新丽鞭毛虫的XynA木聚糖酶相似的催化特性。到目前为止，这些特征在其他环境的细菌中并不普遍存在，这可能表明在瘤胃的高度竞争环境中对这种结构域结构进行了特定选择。
