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产香β-胡萝卜素双加氧酶挖掘与功能验证及酶学性质分析

Discovery, functional verification and enzymatic properties of β-carotene dioxygenases with aroma-producing capability

  • 摘要: 为了筛选能够特异性降解β-胡萝卜素产生香气物质的类胡萝卜素裂解双加氧酶(Carotenoid cleavage dioxygenases,CCDs),基于矮牵牛(Petunia hybrida)PhCCD1蛋白序列,采用结构相似性搜索的生物信息学方法,从公共宏蛋白组MGnify数据库中挖掘到10个新的候选CCDs。通过大肠杆菌异源表达系统对11个CCD重组蛋白进行表达验证,结果显示9个可以成功表达,其中PhCCD1和CCD-11两个蛋白能够可溶性表达。体外酶活分析表明,PhCCD1和CCD-11对β-胡萝卜素和玉米黄质具有较强的降解活性。气相色谱-质谱(Gas chromatography-mass spectrometry,GC-MS)分析结果显示,PhCCD1和CCD-11能够在体外催化β-胡萝卜素产生β-紫罗兰酮,产量分别可达637.35和523.92 μg/mL。此外,二者还能降解番茄红素。进一步的酶学性质研究表明,CCD-11最适温度为50 ℃,最适pH值为5.0,Fe2+和吐温-80可显著提高其酶活性,米氏常数(Km)为4.60 mol/L,酶促最大反应速率(Vmax)为3.47 μmol/(min·mg)。新发现的CCD-11具有能够产生香气物质β-紫罗兰酮的特性,为其在烟草增香等领域的应用奠定了研究基础。

     

    Abstract: To screen carotenoid cleavage dioxygenases (CCDs) specifically capable of degrading β-carotene to produce aroma substances, a bioinformatic search based on structural similarity was employed with Petunia hybrida PhCCD1 as the reference sequence, 10 novel CCDs candidates were identified from the public metaproteomic database MGnify. Heterologous expression in Escherichia coli confirmed successful production of 9 out of 11 recombinant CCD proteins, with PhCCD1 and CCD-11 exhibiting soluble expression. In vitro enzymatic results showed that both PhCCD1 and CCD-11 displayed strong degradation activity toward β-carotene and zeaxanthin. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that these enzymes catalyzed the cleavage production of β-ionone from β-carotene, with yields reaching 637.35 and 523.92 μg/mL, respectively. In addition, both enzymes demonstrated lycopene degradation capability. Further characterization showed that CCD-11 demonstrated optimal activity at 50 ℃ with a pH value of 5.0, and its enzymatic activity was significantly enhanced by Fe2+ and Tween-80. The Michaelis constant (Km) of CCD-11 was 4.60 mol/L, and the maximum enzymatic reaction rate (Vmax) was 3.47 μmol/(min·mg). This study demonstrates that the novel CCD-11 possesses the ability to produce the aroma substance β-ionone, providing a research foundation for its application in tobacco aroma enhancement.

     

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