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首页> 外文期刊>Biochemistry >Discovery of a Novel L-Lyxonate Degradation Pathway in Pseudomonas aeruginosa PAO1
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Discovery of a Novel L-Lyxonate Degradation Pathway in Pseudomonas aeruginosa PAO1

机译：铜绿假单胞菌PAO1中的新型L-Lyxonate降解途径的发现。

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The L-lyxonate dehydratase (LyxD) in vitro enzymatic activity and in vivo metabolic function were assigned to members of an isofunctional family within the mandelate racemase (MR) subgroup of the enolase superfamily. This study combined in vitro and in vivo data to confirm that the dehydration of L-lyxonate is the biological role of the members of this family. In vitro kinetic experiments revealed catalytic efficiencies of ～10~4 M~(?1) s~(?1) as previously observed for members of other families in the MR subgroup. Growth studies revealed that L-lyxonate is a carbon source for Pseudomonas aeruginosa PAO1; transcriptomics using qRT-PCR established that the gene encoding LyxD as well as several other conserved proximal genes were upregulated in cells grown on L-lyxonate. The proximal genes were shown to be involved in a pathway for the degradation of L-lyxonate, in which the first step is dehydration by LyxD followed by dehydration of the 2-keto-3-deoxy-L-lyxonate product by 2-keto-3-deoxy-L-lyxonate dehydratase to yield α-ketoglutarate semialdehyde. In the final step, α-ketoglutarate semialdehyde is oxidized by a dehydrogenase to α-ketoglutarate, an intermediate in the citric acid cycle. An X-ray structure for the LyxD from Labrenzia aggregata IAM 12614 with Mg~(2+) in the active site was determined that confirmed the expectation based on sequence alignments that LyxDs possess a conserved catalytic His-Asp dyad at the end of seventh and sixth β-strands of the (β/α)7β-barrel domain as well as a conserved KxR motif at the end of second β-strand; substitutions for His 316 or Arg 179 inactivated the enzyme. This is the first example of both the LyxD function in the enolase superfamily and a pathway for the catabolism of L-lyxonate.
机译：将L-Lyxonate脱水酶（LyxD）的体外酶活性和体内代谢功能分配给烯醇酶超家族的扁桃体消旋酶（MR）亚组内的同功能家族成员。这项研究结合了体内和体外数据，证实L-lyxonate的脱水是该家族成员的生物学作用。体外动力学实验表明，如先前在MR亚组中其他家族的成员所观察到的，催化效率为〜10〜4 M〜（？1）s〜（？1）。生长研究表明，L-Lyxonate是铜绿假单胞菌PAO1的碳源。使用qRT-PCR进行的转录组学研究证实，在L-Lyxonate上生长的细胞中，编码LyxD的基因以及其他几个保守的近端基因被上调。已证明近端基因参与了L-Lyxonate的降解途径，其中第一步是通过LyxD脱水，然后是2-keto-3-deoxy-L-Lyxonate产物通过2-keto-脱水。 3-deoxy-L-Lyxonate脱水酶产生α-酮戊二酸半醛。在最后一步中，α-酮戊二酸半醛被脱氢酶氧化为α-酮戊二酸，这是柠檬酸循环的中间体。确定了在活动位点上带有Mg〜（2+）的集合体Labenzia aaggregata IAM 12614的LyxD的X射线结构，该序列基于序列比对证实了期望，即LyxDs在第7位和第7位末尾具有保守的催化His-Asp dyad。 （β/α）7β-桶结构域的第六个β链，以及在第二个β链末端的保守的KxR基序; His 316或Arg 179的取代使酶失活。这是烯醇酶超家族中LyxD功能和L-Lyxonate分解代谢途径的第一个例子。

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