Kim Ok Bin, Lux Sebastian, Unden Gottfried
Institut für Mikrobiologie und Weinforschung, Universität Mainz, Becherweg 15, 55099 Mainz, Germany.
Arch Microbiol. 2007 Dec;188(6):583-9. doi: 10.1007/s00203-007-0279-9. Epub 2007 Jul 21.
Escherichia coli is able to grow under anaerobic conditions on D: -tartrate when glycerol is supplied as an electron donor (D-tartrate fermentation). D-Tartrate was converted to succinate. Growth was lost in strains deficient for DcuB, the fumarate/succinate antiporter of fumarate respiration. The L-tartrate/succinate antiporter TtdT of L-tartrate fermentation, or the C4-dicarboxylate carriers DcuA and DcuC, were not able to support D-tartrate transport and fermentation. Deletion of fumB demonstrated, that fumarase B is required for growth on D-tartrate. The mutant lost most (about 79%) of D-tartrate dehydratase activity. L-Tartrate dehydratase (TtdAB), and fumarase A or C, showed no or only a small contribution to D-tartrate dehydratase activity. Therefore D-tartrate is metabolised by a sequence of reactions analogous to that from L-tartrate fermentation, including dehydration to oxaloacetate, which is then converted to malate, fumarate and succinate. The stereoisomer specific carrier TtdT and dehydratase TtdAB of L-tartrate fermentation are substituted by enzymes from general anaerobic fumarate metabolism, the antiporter DcuB and fumarase B, which have a broader substrate specificity. No D-tartrate specific carriers and enzymes are involved in the pathway.
当提供甘油作为电子供体时，大肠杆菌能够在厌氧条件下利用D-酒石酸盐生长（D-酒石酸盐发酵）。D-酒石酸盐被转化为琥珀酸盐。在缺乏DcuB（延胡索酸呼吸的延胡索酸/琥珀酸反向转运蛋白）的菌株中生长能力丧失。L-酒石酸盐发酵的L-酒石酸盐/琥珀酸反向转运蛋白TtdT，或C4-二羧酸载体DcuA和DcuC，均无法支持D-酒石酸盐的转运和发酵。fumB基因的缺失表明，在D-酒石酸盐上生长需要延胡索酸酶B。该突变体丧失了大部分（约79%）的D-酒石酸盐脱水酶活性。L-酒石酸盐脱水酶（TtdAB）以及延胡索酸酶A或C，对D-酒石酸盐脱水酶活性没有贡献或仅有很小的贡献。因此，D-酒石酸盐通过与L-酒石酸盐发酵类似的一系列反应进行代谢，包括脱水生成草酰乙酸，然后草酰乙酸转化为苹果酸、延胡索酸和琥珀酸。L-酒石酸盐发酵的立体异构体特异性载体TtdT和脱水酶TtdAB被来自一般厌氧延胡索酸代谢的酶所取代，即反向转运蛋白DcuB和延胡索酸酶B，它们具有更广泛的底物特异性。该途径中不涉及D-酒石酸盐特异性的载体和酶。
