Mesaconase Activity of Class I Fumarase Contributes to Mesaconate Utilization by Burkholderia xenovorans
Mesaconase Activity of Class I Fumarase Contributes to Mesaconate Utilization by Burkholderia xenovorans
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DOI：
10.1128/aem.00822-15
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发表时间：
2015-08-01
影响因子：
4.4
通讯作者：
Berg, Ivan A.
中科院分区：
文献类型：
--
作者：
Kronen, Miriam;Sasikaran, Jahminy;Berg, Ivan A.
铜绿假单胞菌、鼠疫耶尔森氏菌和许多其他细菌都能够利用 C-5-二羧酸衣康酸酯（亚甲基琥珀酸酯）。衣康酸降解首先被激活为衣康酰辅酶 A（衣康酰辅酶 A），进一步水合为 (S)-柠檬酰辅酶 A，柠檬酰辅酶 A 最终裂解为乙酰辅酶 A 和丙酮酸。异生素降解β变形菌Burkholderia xenovorans拥有类似铜绿假单胞菌的衣康酸降解基因簇，并且能够在衣康酸及其异构体中康酸（富马酸甲酯）上生长。尽管衣康酸降解在异食芽孢杆菌中以与铜绿假单胞菌相同的方式进行，但中康酸的利用途径尚不清楚。在这里，我们表明中康酸通过水合作用代谢为 (S)-柠苹果酸。然后，后一种化合物在衣康酸降解途径的两种酶的参与下代谢为乙酰辅酶A和丙酮酸，这是一种混杂的衣康酸辅酶A转移酶，除了衣康酸和(S)-柠檬酸辅酶A裂解酶之外，还能够激活(S)-柠苹果酸。该途径的第一个反应是中康酸水合酶（mesaconase）反应，由 I 类延胡索酸酶催化。由于这种酶 (Bxe_A3136) 对于富马酸和中康酸水合具有相似的效率 (k(cat)/K-m)，因此我们得出结论，B. xenovorans I 类延胡索酶实际上是混杂的延胡索酸酶/中康酸酶。这种混杂性具有生理相关性，因为它允许这种细菌在中康酸上生长，作为唯一的碳和能源。
Pseudomonas aeruginosa, Yersinia pestis, and many other bacteria are able to utilize the C-5-dicarboxylic acid itaconate (methylenesuccinate). Itaconate degradation starts with its activation to itaconyl coenzyme A (itaconyl-CoA), which is further hydrated to (S)-citramalyl-CoA, and citramalyl-CoA is finally cleaved into acetyl-CoA and pyruvate. The xenobiotic-degrading betaproteobacterium Burkholderia xenovorans possesses a P. aeruginosa-like itaconate degradation gene cluster and is able to grow on itaconate and its isomer mesaconate (methylfumarate). Although itaconate degradation proceeds in B. xenovorans in the same way as in P. aeruginosa, the pathway of mesaconate utilization is not known. Here, we show that mesaconate is metabolized through its hydration to (S)-citramalate. The latter compound is then metabolized to acetyl-CoA and pyruvate with the participation of two enzymes of the itaconate degradation pathway, a promiscuous itaconate-CoA transferase able to activate (S)-citramalate in addition to itaconate and (S)-citramalyl-CoA lyase. The first reaction of the pathway, the mesaconate hydratase (mesaconase) reaction, is catalyzed by a class I fumarase. As this enzyme (Bxe_A3136) has similar efficiencies (k(cat)/K-m) for both fumarate and mesaconate hydration, we conclude that B. xenovorans class I fumarase is in fact a promiscuous fumarase/ mesaconase. This promiscuity is physiologically relevant, as it allows the growth of this bacterium on mesaconate as a sole carbon and energy source.