Dealing with methionine/homocysteine sulfur: cysteine metabolism to taurine and inorganic sulfur.
Dealing with methionine/homocysteine sulfur: cysteine metabolism to taurine and inorganic sulfur.
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DOI：
10.1007/s10545-009-9006-9
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发表时间：
2011-02
影响因子：
4.2
通讯作者：
Ueki, Iori
中科院分区：
文献类型：
--
作者：
Stipanuk, Martha H.;Ueki, Iori
半胱氨酸的合成作为硫磺转化途径的产物，可被视为蛋氨酸或同型半胱氨酸降解的一部分，半胱氨酸是硫磺转化为最终产物(硫酸盐、牛磺酸)的载体，可在尿液中排泄。硫磺的转化是通过刺激胱硫氨酸β合成酶和抑制亚甲基四氢叶酸还原酶来调节的，以响应S-腺苷蛋氨酸水平的变化，这在蛋氨酸可利用性较高的情况下促进了同型半胱氨酸的降解。半胱氨酸是通过几个脱硫反应分解的，这些反应以还原的氧化态释放硫，生成硫烷硫或硫化氢(H2S)，后者可以进一步氧化为硫酸盐。半胱氨酸的脱除是由胱硫醚β合成酶和胱硫氨酸γ裂解酶催化的交替反应完成的。半胱氨酸的分解也需要半胱氨酸硫醇被半胱氨酸双加氧酶初始氧化生成半胱氨酸亚磺酸盐。氧化途径产生牛磺酸和硫酸盐的比例约为2：1。半胱氨酸的相对代谢受半胱氨酸双加氧酶活性的影响，在饲喂低蛋白饲料的动物中，半胱氨酸双加氧酶活性较低，而在饲喂过量含硫氨基酸的动物中，半胱氨酸的相对代谢活性较高。因此，当半胱氨酸缺乏时，脱硫反应占主导地位，而当半胱氨酸过剩时，氧化分解代谢占主导地位。在饮食中摄入适量含硫氨基酸的大鼠中，大约三分之二的半胱氨酸分解代谢是通过氧化途径进行的，三分之一是通过脱硫途径进行的。半胱氨酸双加氧酶受半胱氨酸可获得性的强烈调控，其功能可能是提供一条途径，将半胱氨酸虹吸成比半胱氨酸脱硫反应产生的毒性更低的代谢物。
Synthesis of cysteine as a product of the transsulfuration pathway can be viewed as part of methionine or homocysteine degradation, with cysteine being the vehicle for sulfur conversion to end products (sulfate, taurine) that can be excreted in the urine. Transsulfuration is regulated by stimulation of cystathionine β-synthase and inhibition of methylene tetrahydrofolate reductase in response to changes in the level of S-adenosylmethionine, and this promotes homocysteine degradation when methionine availability is high. Cysteine is catabolized by several desulfuration reactions that release sulfur in a reduced oxidation state, generating sulfane sulfur or hydrogen sulfide (H2S), which can be further oxidized to sulfate. Cysteine desulfuration is accomplished by alternate reactions catalyzed by cystathionine β-synthase and cystathionine γ-lyase. Cysteine is also catabolized by pathways that require the initial oxidation of the cysteine thiol by cysteine dioxygenase to form cysteinesulfinate. The oxidative pathway leads to production of taurine and sulfate in a ratio of approximately 2:1. Relative metabolism of cysteine by desulfuration versus oxidative pathways is influenced by cysteine dioxygenase activity, which is low in animals fed low-protein diets and high in animals fed excess sulfur amino acids. Thus, desulfuration reactions dominate when cysteine is deficient, whereas oxidative catabolism dominates when cysteine is in excess. In rats consuming a diet with an adequate level of sulfur amino acids, about two thirds of cysteine catabolism occurs by oxidative pathways and one third by desulfuration pathways. Cysteine dioxygenase is robustly regulated in response to cysteine availability and may function to provide a pathway to siphon cysteine to less toxic metabolites than those produced by cysteine desulfuration reactions.
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影响因子：
4.8
作者：
Chiku, Taurai;Padovani, Dominique;Banerjee, Ruma
通讯作者：
Banerjee, Ruma
影响因子：
2.8
作者：
CRAWHALL, JC
通讯作者：
CRAWHALL, JC
DOI：
10.1152/ajpendo.00053.2007
发表时间：
2007-07-01
影响因子：
5.1
作者：
Dominy, John E., Jr.;Hwang, Jesse;Stipanuk, Martha H.
通讯作者：
Stipanuk, Martha H.
影响因子：
4.2
作者：
Bella, DL;Kwon, YH;Stipanuk, MH
通讯作者：
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影响因子：
--
作者：
COLOSO, RM;DRAKE, MR;STIPANUK, MH
通讯作者：
STIPANUK, MH