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首页> 外文期刊>Applied and Environmental Microbiology >Purification and some properties of riboflavin synthetase from Bacillus stearothermophilus ATCC 8005.
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Purification and some properties of riboflavin synthetase from Bacillus stearothermophilus ATCC 8005.

机译：嗜热脂肪芽孢杆菌ATCC 8005的核黄素合成酶的纯化和某些性质。

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A riboflavin synthetase was purified 51-fold from a thermophilic organism, Bacillus stearothermophilus ATCC 8005, that grew at 40 to 72 degrees C. Some of the properties of the enzyme are: (i) its temperature optimum was 95 degrees C, and the activity was negligible below 40 degrees C; (ii) the Arrhenius plot of the initial reaction rates was concave upward, with a break at 65 degrees C, and the apparent activation energies below and above 65 degrees C were 4.2 X 10(4) and 6.7 X 10(4) J/mol, respectively; (iii) the enzyme was fairly stable up to 60 degrees C without 6,7-dimethyl-8-ribityllumazine; this substance protected the enzyme from inactivation above 60 to 97 degrees C; (iv) the pH range for stability was 6.0 to 10.0 at 26 degrees C and 6.3 to 7.6 at 55 degrees C; (v) the enzyme was highly resistant at 26 degrees C to denaturation in 8 M urea, but the tolerance was extremely low at 55 degrees C; (vi) its molecular weight was estimated at 45,000; (vii) the Km for 6,7-dimethyl-8-ribityllumazine was 23 micrometer at 55 degrees C and 29 micrometer at 75 degrees C; (viii) its pH optimum was 6.7 to 7.2; (ix) 6-methyl-7-hydroxy-8-ribityllumazine was a competitive inhibitor (Ki = 0.18 micrometer); (x) the activity was sensitive to heavy-metal ions and thiol reagents; (xi) the enzyme did not require cofactor or a carbon donor; and (xii) the molar ratio of 6,7-dimethyl-8-ribityllumazine consumption to riboflavin formation was 2 throughout the entire reaction. Properties i through vi distinguish this enzyme from riboflavin synthetases purified by other investigators from mesophilic organisms, Ashbya gossypii, Eremothecium ashbyii, Escherichia coli, yeast, and spinach.
机译：从嗜热芽孢杆菌嗜热脂肪芽孢杆菌ATCC 8005纯化51倍的核黄素合成酶，该菌在40至72摄氏度下生长。该酶的某些特性是：（i）最适温度为95摄氏度，且活性在40摄氏度以下可以忽略不计; （ii）初始反应速率的Arrhenius曲线向上凹，在65摄氏度时断裂，低于和高于65摄氏度的表观活化能分别为4.2 X 10（4）和6.7 X 10（4）J /摩尔分别（iii）所述酶在没有60,7-二甲基-8-ribityllumazine的条件下在60摄氏度下相当稳定;该物质可防止酶在60至97摄氏度以上失活; （iv）稳定性的pH范围在26摄氏度时为6.0至10.0，在55摄氏度时为6.3至7.6; （v）该酶在26℃下对8M尿素中的变性具有很高的抵抗力，但在55℃下的耐受性极低; （vi）其分子量估计为45,000; （vii）6,7-二甲基-8-核苷二嗪的Km在55℃下为23微米，在75℃下为29微米; （viii）其最适pH为6.7至7.2; （ix）6-甲基-7-羟基-8-核苷二嗪是竞争性抑制剂（Ki = 0.18微米）; （x）活性对重金属离子和硫醇试剂敏感; （xi）该酶不需要辅因子或碳供体; （xii）在整个反应过程中6，7-二甲基-8-核苷二嗪消耗量与核黄素形成的摩尔比为2。特性i至vi将该酶与由其他研究者从嗜温生物，棉兰阿什比棉，阿什莫氏假丝酵母，大肠埃希氏菌，酵母和菠菜中纯化的核黄素合成酶区分开。

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