A novel thermophilic endoglucanase from a mesophilic fungus Fusarium oxysporum  

作　　者：LIU Shuyan DUAN Xinyuan LU Xuemei GAO Peiji 

机构地区：[1]State Key Laboratory of Microbial Technology, Shandong University, Ji'nan 250100, China

出　　处：《Chinese Science Bulletin》2006年第2期191-197,共7页

基　　金：We acknowledge the help of Robert Koebner in the linguistic correction of the manuscript.This work was supported by the National Natural Science Foundation of China(Grants Nos.30370013&30470051);the Major State Basic Research Development Research Program of China("973"Project)(Grant Nos.2003CB716006&2004CB719702).

摘　　要：A novel thermophilic endoglucanase (EGt) was extracted from a mesophilic fungus (Fusarium oxysporum L19). We invoked conventional kinetic enzyme reactions using the sodium salt of carboxymethyl cellulose (CMC-Na) as substrate. EGt displayed optimal activity at 75℃ when kept running 30 min in the temperature range of 30―85℃. Thermal stability curve measured at 70℃ suggested that its half-life time is 15.1 min. The activity was enhanced in the presence of Co2+ or Mg2+ but inhibited by Pb2+ and Fe3+. 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. Amino acid composition analysis demonstrated that EGt contains more proline residues. EGt lacks activity towards p-nitro- phenyl cellobiose (pNPC). The N-terminal amino acid se- quence of EGt is SYRVPAANGFPNPDASQEKQ, and the gene of EGt was sequenced and analyzed. Extensive se- quence 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 ex- pression of multiple isoenzyme in an organism helps it adapt to complex living environments.A novel thermophilic endoglucanase （EGt） was extracted from a mesophilic fungus （Fusarium oxysporum L19）. We invoked conventional kinetic enzyme reactions using the sodium salt of carboxymethyl cellulose （CMC-Na） as substrate. EGt displayed optimal activity at 75℃ when kept running 30 min in the temperature range of 30-85℃. Thermal stability curve measured at 70℃ 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 Pbo^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. Amino acid composition analysis demonstrated that EGt contains more proline residues. EGt lacks activity towards p-nitrophenyl 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.

关 键 词：嗜温菌 尖镰孢 香蕉 枯萎病 嗜热葡聚糖内切酶 热稳定性 热活性 

分 类 号：S436.67[农业科学—农业昆虫与害虫防治]