Senescence marker protein 30 functions as gluconolactonase in L-ascorbic acid biosynthesis, and its knockout mice are prone to scurvy
Senescence marker protein 30 functions as gluconolactonase in L-ascorbic acid biosynthesis, and its knockout mice are prone to scurvy
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DOI：
10.1073/pnas.0511225103
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发表时间：
2006-04-11
影响因子：
11.1
通讯作者：
Ishigami, A
中科院分区：
文献类型：
--
作者：
Kondo, Y;Inai, Y;Ishigami, A
我们最初将衰老标记蛋白30（SMP30）鉴定为一种独特的蛋白质，其表达随着衰老以雄激素非依赖性方式降低。在这里，我们报告了它的序列同源性发现在两种细菌的β-内酯酶（GNLs），通过使用BLAST搜索。然后，通过生物化学研究，我们确定SMP 30为动物物种的内酯水解酶GNL。从大鼠肝脏中纯化的SMP 30对各种醛内酯具有内酯酶活性，如D-和L-β-δ-内酯、D-和L-古洛糖酸-γ-内酯以及D-和L-半乳糖酸-γ-内酯，需要Zn 2+或Mn 2+作为辅因子。此外，在SMP30敲除小鼠中，在肝脏中未检测到GNL活性。因此，我们得出结论，SMP30是肝脏中唯一的GNL。内酯酶与L-古洛糖酸-γ-内酯的反应是L-抗坏血酸（AA）生物合成的倒数第二步，并且在此通过使用SMP30敲除小鼠的营养研究验证了SMP30在该合成过程中的重要作用。这些敲除小鼠（n = 6），喂食维生素C缺乏的饮食，没有茁壮成长;即，他们表现出坏血病的症状，如骨折和佝偻病念珠，然后在开始接受缺乏饮食后135天死亡。死亡时肝脏和肾脏中的AA水平<WT对照小鼠的1.6%。此外，通过使用SMP30基因敲除小鼠，我们证明了涉及D-葡萄糖醛酸-γ-内酯的AA合成的替代途径在体内运作，尽管其通量相当小。
We originally identified senescence marker protein 30 (SMP30) as a distinctive protein whose expression decreases in an androgen-independent manner with aging. Here, we report its sequence homology found in two kinds of bacterial gluconolactonases (GNLs) by using the BLAST search. Then, through a biochemical study, we identify SMP30 as the lactone-hydrolyzing enzyme GNL of animal species. SMP30 purified from the rat liver had lactonase activity toward various aldonolactones, such as D- and L-glucono-delta-lactone, D- and L-gulono-gamma-lactone, and D- and L-galactono-gamma-lactone, with a requirement for Zn2+ or Mn2+ as a cofactor. Furthermore, in SMP30 knockout mice, no GNL activity was detectable in the liver. Thus, we conclude that SMP30 is a unique GNL in the liver. The lactonase reaction with L-gulono-gamma-lactone is the penultimate step in L-ascorbic acid (AA) biosynthesis, and the essential role of SMP30 in this synthetic process was verified here by a nutritional study using SMP30 knockout mice. These knockout mice (n = 6), fed a vitamin C-deficient diet, did not thrive; i.e., they displayed symptoms of scurvy such as bone fracture and rachitic rosary and then died by 135 days after the start of receiving the deficient diet. The AA levels in their livers and kidneys at the time of death were < 1.6% of those in WT control mice. In addition, by using the SMP30 knockout mouse, we demonstrate that the alternative pathway of AA synthesis involving D-glucurono-gamma-lactone operates in vivo, although its flux is fairly small.