链霉菌属产尿酸氧化酶菌株的筛选、异源表达及重组酶性质研究

Screening of urate oxidase-producing Streptomyces strains, gene cloning and heterogeneous expression, and characterization of the recombinant enzyme

  • 摘要: 尿酸氧化酶能够催化尿酸分解为过氧化氢以及溶解性更强的尿囊素,常用于尿酸检测和治疗高尿酸引发的相关疾病. 本研究从青海省茶卡盐湖的湖泊沉积物中筛选出1株高产尿酸氧化酶菌株2YHDJ-2,经16S rRNA基因测序和系统发育分析,将其确定为链霉菌属(Streptomyces sp.). 根据GenBank中已知尿酸氧化酶基因保守序列设计简并引物进行PCR扩增,获得长度为952 bp的尿酸氧化酶基因,与已报道的Streptomyces sp. strain NSC9来源尿酸氧化酶基因同源性高达99%. 将该基因构建至pET-15b载体并转化至大肠杆菌BL21(DE3)异源表达,获得相对分子质量约38 ku的重组酶. 酶学性质研究表明,该重组酶的最佳反应pH和温度分别为5.0和20 ℃. 具有较好的pH耐受性和温度耐受性,在pH 3.0 ~ 8.0范围内处理12 h,在15 、20 、25 ℃和37 ℃温度下处理100 min,仍能够保持超过60%的相对活性. 在近人体生理温度(37 ℃)条件下稳定性较好. 且K+,Mg2+和Zn2+对该酶酶活有一定的促进作用,可将酶活提高至120%以上. 以上研究结果表明,Streptomyces sp. 2YHDJ-2来源的尿酸氧化酶兼具宽泛的pH和温度适应性,稳定性较好,为开发高灵敏尿酸检测试剂及新型尿酸氧化酶制剂提供了实验依据和菌种资源.

     

    Abstract: Urate oxidase catalyzes the decomposition of uric acid into hydrogen peroxide and the more highly soluble allantoin. It is commonly used for uric acid detection and the treatment of diseases related to hyperuricemia. In this study, a high-yielding urate oxidase strain, 2YHDJ-2, was isolated from the lake sediments of Chaka Salt Lake in Qinghai Province. Through 16S rRNA gene sequencing and phylogenetic analysis, it was identified as Streptomyces sp. Degenerate primers were designed based on the conserved sequences of known urate oxidase genes in GenBank for PCR amplification, yielding a 952 bp urate oxidase gene. This gene shares up to 99% homology with the reported urate oxidase gene from Streptomyces sp. strain NSC9. The gene was cloned into the pET-15b vector and transformed into Escherichia coli BL21(DE3) for heterologous expression, resulting in a recombinant enzyme with an approximate molecular weight of 38 kDa. Enzymatic characterization revealed that the recombinant enzyme exhibited optimal activity at pH 5.0 and 20 ℃. Furthermore, the enzyme demonstrated broad pH and temperature tolerance, retaining over 60% of its relative activity after incubation at pH 3.0–8.0 for 12 h, or at 15, 20, 25, and 37 ℃ for 100 min. Notably, it exhibited robust stability near the human physiological temperature (37 ℃). The addition of K+, Mg2+, and Zn2+ significantly enhanced the enzyme's activity to over 120% of its initial level. These findings indicate that the urate oxidase derived from Streptomyces sp. 2YHDJ-2 possesses broad pH and temperature adaptability alongside high stability. This study provides a promising microbial resource and a strong experimental basis for developing highly sensitive uric acid diagnostic reagents and novel urate oxidase preparations.

     

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