Sato Y, Yamamoto Y, Kizaki H, Kuramitsu H K
Department of Biochemistry, Tokyo Dental College, Chiba City, Japan.
FEMS Microbiol Lett. 1993 Nov 15;114(1):61-6. doi: 10.1111/j.1574-6968.1993.tb06551.x.
A gene encoding a phosphomannose isomerase from Streptococcus mutans GS-5 was identified immediately downstream from the fructokinase gene, scrK. Nucleotide sequence analysis of this region revealed an open reading frame (ORF) specifying a putative protein of 316 amino acids. The gene cloned in Escherichia coli expressed strong phosphomannose isomerase activity. The deduced amino acid sequence of the pmi gene has no significant similarity with any of the previously reported phosphomannose isomerase enzymes. Insertional inactivation of the upstream gene, scrK, in S. mutans also drastically reduced phosphomannose isomerase activity and the ability of the organism to utilize mannose as a sole carbon source. These results suggest that the S. mutans pmi gene constitutes an operon with the scrK gene.
在变形链球菌GS-5中，一个编码磷酸甘露糖异构酶的基因紧挨着果糖激酶基因scrK被鉴定出来，位于其下游。对该区域的核苷酸序列分析揭示了一个开放阅读框（ORF），它编码一个由316个氨基酸组成的假定蛋白质。克隆到大肠杆菌中的该基因表达出很强的磷酸甘露糖异构酶活性。pmi基因推导的氨基酸序列与之前报道的任何磷酸甘露糖异构酶均无显著相似性。变形链球菌中上游基因scrK的插入失活也极大地降低了磷酸甘露糖异构酶的活性以及该生物体利用甘露糖作为唯一碳源的能力。这些结果表明，变形链球菌的pmi基因与scrK基因构成一个操纵子。
