Kornberg H L
Department of Biology, Boston University, MA 02215, USA.
J Mol Microbiol Biotechnol. 2001 Jul;3(3):355-9.
There are three main routes for the utilization of fructose by Escherichia coli. One (Route A) predominates in the growth of wild-type strains. It involves the functioning of the phosphoenolpyruvate:glycose phosphotransferase system (PTS) and a fructose operon, mapping at min. 48.7, containing genes for a membrane-spanning protein (fruA), a 1-phosphofructose kinase (fruK) and a diphosphoryl transfer protein (fruB), under negative regulation by a fruR gene mapping at min. 1.9. A second route (Route B) also involves the PTS and membrane-spanning proteins that recognize a variety of sugars possessing the 3,4,5-D-arabino-hexoseconfiguration but with primary specificity for mannose(manXYZ), mannitol (mtlA) and glucitol (gutA) and which, if over-produced, can transport also fructose. A third route (Route C), functioning in mutants devoid of Routes A and B, does not involve the PTS: fructose diffuses into the cell via an isoform (PtsG-F) of the major glucose permease of the PTS and is then phosphorylated by ATP and a manno(fructo)kinase (Mak+) specified by a normally cryptic 1032 bp ORF (yajF) of hitherto unknown function (Mak-o), mapping at min. 8.8 and corresponding to a peptide of 344 amino acids. Conversion of the Mak-o to the Mak+ phenotypeinvolves an A24D mutation in a putative regulatory region.
大肠杆菌利用果糖主要有三条途径。其中一条途径（途径A）在野生型菌株生长中占主导地位。它涉及磷酸烯醇丙酮酸：葡萄糖磷酸转移酶系统（PTS）和一个果糖操纵子的作用，该操纵子位于48.7分钟处，包含编码跨膜蛋白（fruA）、1-磷酸果糖激酶（fruK）和二磷酸转移蛋白（fruB）的基因，受位于1.9分钟处的fruR基因的负调控。第二条途径（途径B）也涉及PTS和跨膜蛋白，这些蛋白能识别具有3,4,5-D-阿拉伯己糖构型的多种糖类，但对甘露糖（manXYZ）、甘露醇（mtlA）和葡糖醇（gutA）具有主要特异性，并且如果过量产生，也能转运果糖。第三条途径（途径C）在缺乏途径A和B的突变体中起作用，不涉及PTS：果糖通过PTS主要葡萄糖通透酶的一种同工型（PtsG-F）扩散进入细胞，然后被ATP和一种甘露（果糖）激酶（Mak+）磷酸化，该激酶由一个功能未知的1032 bp的正常隐蔽开放阅读框（yajF）（Mak-o）指定，位于8.8分钟处，对应于一个344个氨基酸的肽段。Mak-o向Mak+表型的转变涉及一个推定调控区域中的A24D突变。
