Sulphoglycolysis in Escherichia coli K-12 closes a gap in the biogeochemical sulphur cycle
Sulphoglycolysis in Escherichia coli K-12 closes a gap in the biogeochemical sulphur cycle
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DOI：
10.1038/nature12947
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发表时间：
2014-03-06
期刊：
影响因子：
64.8
通讯作者：
Schleheck, David
中科院分区：
文献类型：
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作者：
Denger, Karin;Weiss, Michael;Schleheck, David
50年来，磺基喹诺糖（SQ，6-脱氧-6-磺基葡萄糖）一直被认为是所有高等植物、苔藓、蕨类植物、藻类和大多数光合细菌（3）的光合膜中植物硫脂（1，2）的极性头基。它也存在于一些非光合细菌中（4），SQ是某些细菌表层的一部分（5）。SQ（4）的估计年产量为10，000，000，000吨（10千万亿克），因此它构成了自然界中有机硫的主要部分，其中SQ被细菌降解（6，7）。然而，尽管有证据表明细菌中存在至少三种不同的降解途径（6-8），但尚未确定任何途径中的酶反应或基因，尽管已提出了磺基糖酵解途径（7）。在这里，我们表明，大肠杆菌K-12，最广泛研究的原核模式生物，进行磺基糖酵解，除了标准的糖酵解。SQ通过我们使用纯化的异源表达酶建立的四种新发现的反应分解代谢：SQ异构酶，6-脱氧-6-磺基果糖（SF）激酶，6-脱氧-6-磺基果糖-1-磷酸（SFP）醛缩酶和3-磺基乙醛（SLA）还原酶。该酶编码于一个10基因簇中，该基因簇可能也编码整个硫脂的调节、运输和降解，该基因簇存在于几乎所有（>91%）可用的E.大肠杆菌基因组，并广泛分布在肠杆菌科。该途径产生磷酸二羟丙酮（DHAP），为E.大肠杆菌，和磺酸盐产物2，3-二羟基丙烷-1-磺酸盐（DHPS），这是排泄。DHPS被其他细菌矿化，从而关闭细菌群落内的硫循环。
Sulphoquinovose (SQ, 6-deoxy-6-sulphoglucose) has been known for 50 years as the polar headgroup of the plant sulpholipid(1,2) in the photosynthetic membranes of all higher plants, mosses, ferns, algae and most photosynthetic bacteria(3). It is also found in some non-photosynthetic bacteria(4), and SQ is part of the surface layer of some Archaea(5). The estimated annual production of SQ(4) is 10,000,000,000 tonnes (10 petagrams), thus it comprises a major portion of the organo-sulphur in nature, where SQ is degraded by bacteria(6,7). However, despite evidence for at least three different degradative pathways in bacteria(6-8), no enzymic reaction or gene in any pathway has been defined, although a sulphoglycolytic pathway has been proposed(7). Here we show that Escherichia coli K-12, the most widely studied prokaryotic model organism, performs sulphoglycolysis, in addition to standard glycolysis. SQ is catabolised through four newly discovered reactions that we established using purified, heterologously expressed enzymes: SQ isomerase, 6-deoxy-6-sulphofructose (SF) kinase, 6-deoxy-6-sulphofructose-1-phosphate (SFP) aldolase, and 3-sulpholactaldehyde (SLA) reductase. The enzymes are encoded in a ten-gene cluster, which probably also encodes regulation, transport and degradation of the whole sulpholipid; the gene cluster is present in almost all (>91%) available E. coli genomes, and is wide-spread in Enterobacteriaceae. The pathway yields dihydroxyacetone phosphate (DHAP), which powers energy conservation and growth of E. coli, and the sulphonate product 2,3-dihydroxypropane-1-sulphonate (DHPS), which is excreted. DHPS is mineralized by other bacteria, thus closing the sulphur cycle within a bacterial community.