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首页> 外文期刊>Chinese science bulletin >A novel thermophilic endoglucanase from a mesophilic fungus Fusarium oxysporum
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A novel thermophilic endoglucanase from a mesophilic fungus Fusarium oxysporum

机译：一种新的嗜温真菌尖孢镰刀菌的内切葡聚糖酶

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摘要

A novel thermophilic endoglucanase (EGt) was extracted from a mesophilic fungus (Fusarium oxysporum LI9). We invoked conventional kinetic enzyme reactions using the sodium salt of carboxymethyl cellulose (CMC-Na) as substrate. EGt displayed optimal activity at 75 deg C when kept running 30 min in the temperature range of 30-85deg C. Thermal stability curve measured at 70 deg C suggested that its half-life time is 15.1 min. The activity was enhanced in the presence of Co~(2+) or Mg~(2+) but inhibited by Pb~(2+) and Fe~(3+). Moreover, N-bromosuccinimide (NBS) modification resulted in a complete loss of EGt activity, suggesting that tryptophan residues may be involved in the enzyme active site. Ammo acid composition analysis demonstrated that EGt contains more proline residues. EGt lacks activity towards p-nitro-phenyl cellobiose (pNPC). The N-terminal amino acid sequence of EGt is SYRVPAANGFPNPDASQEKQ, and the gene of EGt was sequenced and analyzed. Extensive sequence alignments failed to show any homology between EGt and any known endoglucanases. This is the first report addressing the thermal adaptation of a cellulolytic enzyme from the mesophilic fungus F. oxysporum. Maybe the expression of multiple isoenzyme in an organism helps it adapt to complex living environments.
机译：从嗜温真菌（Fsarium oxysporum LI9）中提取了一种新型的嗜热内切葡聚糖酶（EGt）。我们使用羧甲基纤维素钠盐（CMC-Na）作为底物调用了常规的动力学酶反应。当在30-85摄氏度的温度范围内保持30分钟运行时，EGt在75摄氏度下显示出最佳活性。在70摄氏度下测得的热稳定性曲线表明其半衰期为15.1分钟。在Co〜（2+）或Mg〜（2+）存在下，活性得到增强，但被Pb〜（2+）和Fe〜（3+）抑制。此外，N-溴代琥珀酰亚胺（NBS）修饰导致EGt活性完全丧失，表明色氨酸残基可能参与了酶的活性位点。氨基酸组成分析表明，EGt含有更多的脯氨酸残基。 EGt对对硝基苯基纤维二糖（pNPC）缺乏活性。 EGt的N端氨基酸序列为SYRVPAANGFPNPDASQEKQ，并对EGt的基因进行测序和分析。广泛的序列比对未能显示出EGt与任何已知的内切葡聚糖酶之间的任何同源性。这是第一个针对中温真菌氧化菌F. oxysporum的纤维素分解酶的热适应性报道。也许生物中多种同工酶的表达有助于其适应复杂的生活环境。

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