Research Institute for Photosynthetic Hydrogen Production, Kanagawa University, Hiratsuka, Kanagawa, Japan.
Photosynth Res. 2010 Jun;104(2-3):163-76. doi: 10.1007/s11120-010-9531-2. Epub 2010 Feb 9.
Green sulfur bacteria use various reduced sulfur compounds such as sulfide, elemental sulfur, and thiosulfate as electron donors for photoautotrophic growth. This article briefly summarizes what is known about the inorganic sulfur oxidizing systems of these bacteria with emphasis on the biochemical aspects. Enzymes that oxidize sulfide in green sulfur bacteria are membrane-bound sulfide-quinone oxidoreductase, periplasmic (sometimes membrane-bound) flavocytochrome c sulfide dehydrogenase, and monomeric flavocytochrome c (SoxF). Some green sulfur bacteria oxidize thiosulfate by the multienzyme system called either the TOMES (thiosulfate oxidizing multi-enzyme system) or Sox (sulfur oxidizing system) composed of the three periplasmic proteins: SoxB, SoxYZ, and SoxAXK with a soluble small molecule cytochrome c as the electron acceptor. The oxidation of sulfide and thiosulfate by these enzymes in vitro is assumed to yield two electrons and result in the transfer of a sulfur atom to persulfides, which are subsequently transformed to elemental sulfur. The elemental sulfur is temporarily stored in the form of globules attached to the extracellular surface of the outer membranes. The oxidation pathway of elemental sulfur to sulfate is currently unclear, although the participation of several proteins including those of the dissimilatory sulfite reductase system etc. is suggested from comparative genomic analyses.
绿色硫细菌利用各种还原态硫化合物，如硫化物、单质硫和硫代硫酸盐作为电子供体进行光自养生长。本文简要总结了这些细菌无机硫氧化系统的已知情况，重点介绍了生物化学方面。氧化绿色硫细菌中的硫化物的酶是膜结合的硫化物-醌氧化还原酶、周质（有时是膜结合的）黄素细胞色素 c 硫化物脱氢酶和单体黄素细胞色素 c（SoxF）。一些绿色硫细菌通过称为 TOMES（硫代硫酸盐氧化多酶系统）或 Sox（硫氧化系统）的多酶系统氧化硫代硫酸盐，该系统由三种周质蛋白组成：SoxB、SoxYZ 和 SoxAXK 以及可溶性小分子细胞色素 c 作为电子受体。这些酶在体外氧化硫化物和硫代硫酸盐时假定产生两个电子，并导致硫原子转移到过硫酸盐中，过硫酸盐随后转化为单质硫。单质硫暂时以附着在外膜细胞外表面的小球体形式储存。尽管从比较基因组分析中提出了包括异化亚硫酸盐还原酶系统等几种蛋白质的参与，但元素硫到硫酸盐的氧化途径目前尚不清楚。
