URATE OXIDASE - PRIMARY STRUCTURE AND EVOLUTIONARY IMPLICATIONS
URATE OXIDASE - PRIMARY STRUCTURE AND EVOLUTIONARY IMPLICATIONS
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DOI：
10.1073/pnas.86.23.9412
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发表时间：
1989-12-01
影响因子：
11.1
通讯作者：
CASKEY, CT
中科院分区：
文献类型：
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作者：
WU, XW;LEE, CC;CASKEY, CT
尿酸氧化酶或尿酸酶(EC 1.7.3.3)是一种过氧化物酶，在大多数哺乳动物中催化尿酸氧化成尿囊素。然而，在人类和其他某些灵长类动物中，这种酶已经因为某种未知的机制而丢失。为了确定这种缺失的分子基础，我们从猪、小鼠和狒狒中分离了尿酸氧化酶基因克隆，并测定了它们的DNA序列。小鼠尿酸氧化酶开放阅读框编码303个氨基酸的多肽，而猪和狒狒的尿酸氧化酶cDNA编码一个304个氨基酸的多肽，这是由于单一密码子缺失/插入事件。通过对该基因的小鼠和猪基因组拷贝进行测序，证实了这一单个额外密码子的真实性。该序列含有与其他铜结合蛋白中发现的2型铜结合基序类似的结构域，表明尿酸氧化酶中的铜离子是以2型结构配位的。根据NH2末端的多肽和推导的序列的比较，我们认为猪尿酸酸氧化酶的成熟涉及一个六个氨基酸的翻译后切割。在人类尿酸氧化酶基因中发现了两个无义突变，这在分子水平上证实了人类的尿酸氧化酶基因是无功能的。序列比较支持这样的假设，即人类尿酸氧化酶的丢失是由于突然的突变事件，而不是渐进的突变过程。
Urate oxidase, or uricase (EC 1.7.3.3), is a peroxisomal enzyme that catalyzes the oxidation of uric acid to allantoin in most mammals. In humans and certain other primates, however, the enzyme has been lost by some unknown mechanism. To identifiy the molecular basis for this loss, urate oxidase cDNA clones were isolated from pig, mouse, and baboon, and their DNA sequences were determined. The mouse urate oxidase open reading frame encodes a 303-amino acid polypeptide, while the pig and baboon urate oxidase cDNAs encode a 304-amino acid polypeptide due to a single codon deletion/insertion event. The authenticity of this single additional codon was confirmed by sequencing the mouse and pig genomic copies of the gene. The urate oxidase sequence contains a domain similar to the type 2 copper binding motif found in other copper binding proteins, suggesting that the copper ion in urate oxidase is coordinated as a type 2 structure. Based upon a comparison of the NH2-terminal peptide and deduced sequences, we propose that the maturation of pig urate oxidase involves the posttranslational cleavage of a six-amino acid peptide. Two nonsense mutations were found in the human urate oxidase gene, which confirms, at the molecular level, that the urate oxidase gene in humans is nonfunctional. The sequence comparisons favor the hypothesis that the loss of urate oxidase in humans is due to a sudden mutational event rather than a progressive mutational process.