Two transsulfurylation pathways in Klebsiella pneumoniae.
Two transsulfurylation pathways in Klebsiella pneumoniae.
复制标题
肺炎克雷伯菌中的两种转硫途径。
DOI：
10.1128/jb.00347-06
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Lawrence,JeffreyG
中科院分区：
文献类型：
--
作者：
Seiflein,ThomasA;Lawrence,JeffreyG
In most bacteria, inorganic sulfur is assimilated into cysteine, which provides sulfur for methionine biosynthesis via transsulfurylation. Here, cysteine is transferred to the terminal carbon of homoserine via its sulfhydryl group to form cystathionine, which is cleaved to yield homocysteine. In the enteric bacteriaEscherichia coliandSalmonella enterica, these reactions are catalyzed by irreversible cystathionine-γ-synthase and cystathionine-β-lyase enzymes. Alternatively, yeast and some bacteria assimilate sulfur into homocysteine, which serves as a sulfhydryl group donor in the synthesis of cysteine by reverse transsulfurylation with a cystathionine-β-synthase and cystathionine-γ-lyase. Herein we report that the related enteric bacteriumKlebsiella pneumoniaeencodes genes for both transsulfurylation pathways; genetic and biochemical analyses show that they are coordinately regulated to prevent futile cycling.Klebsiellauses reverse transsulfurylation to recycle methionine to cysteine during periods of sulfate starvation. Thismethionine-to-cysteine (mtc) transsulfurylation pathway is activated by cysteine starvation via the CysB protein, by adenosyl-phosphosulfate starvation via the Cbl protein, and by methionine excess via the MetJ protein. Whilemtcmutants cannot use methionine as a sulfur source on solid medium, they will utilize methionine in liquid medium via a sulfide intermediate, suggesting that an additional nontranssulfurylation methionine-to-cysteine recycling pathway(s) operates under these conditions.
