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Gene Cloning and Protein Structural Studies of a Glycoside Hydrolase Family 5 Enzyme Gene from Inonotus hispidus

粗毛纤孔菌糖苷水解酶5基因克隆及蛋白质结构分析


【目的】克隆得到粗毛纤孔菌糖苷水解酶5基因,并对该基因进行生物信息学分析、蛋白质原核表达和酶活研究,为糖苷水解酶的利用提供依据。【方法】分离纯化粗毛纤孔菌,并于PDA斜面长期保存。应用TRIzol提取粗毛纤孔菌总RNA,通过AMV反转录系统将RNA反转录成cDNA,构建cDNA文库; 应用NCBI BLAST分析并检测糖苷水解酶基因家族5阳性序列,RACE法克隆基因全长命名为IhGH 5-1 并提交NCBI注册; ORF-Finder分析IhGH 5-1 基因开放阅读框,推导出氨基酸序列; 筛选NCBI登录的糖苷水解酶家族5同源序列,Clustal W进行保守结构域区段多序列比对; 应用Mega 5.05选用WAG+G模型构建最大似然树; 应用PSIPRED server对IhGH5-1进行α螺旋和β折叠的蛋白质二级结构分析,应用SWISS-MODEL对IhGH5-1进行三维建模,应用VMD1.8.6分析IhGH5-1三维结构; 设计原核表达引物并进行PCR扩增,将扩增得到的基因片段连接至pQE-30 UA 载体并转入大肠埃希菌JM109感受态细胞,诱导表达后通过SDS-PAGE电泳检测表达量; 测定糖苷水解酶活性并计算酶活。【结果】TRIzol提取的粗毛纤孔菌总RNA经分光光度计检验符合标准(OD260/OD280=2.0,OD260/OD230>1.8),cDNA文库成功构建并测序; RACE法克隆得到5‘序列长度为770 bp,3‘序列长度为1 562 bp且含有PolyA的序列,5‘和3‘序列拼接得到基因全长序列长1 727 bp, NCBI注册号为KM368321; ORF分析得到IhGH5-1氨基酸序列含有300个氨基酸,分子质量为31.226 55 kD,等电点(pI)为9.24; 结构域分析表明IhGH5-1具有保守的催化结构域; 最大似然树分析表明多数子囊菌糖苷水解酶家族5聚在一起,多数担子菌糖苷水解酶家族5聚在一起,粗毛纤孔菌IhGH5-1蛋白质与太瑞斯梭孢壳霉和球毛壳菌等子囊菌的糖苷水解酶亲缘关系更近; 蛋白质三维结构分析表明粗毛纤孔菌IhGH5-1含有7个α螺旋、4个β折叠,三维比对表明粗毛纤孔菌IhGH5-1三维结构与其他真菌糖苷水解酶家族5蛋白空间结构相近,进化关系与最大似然树分析相符; 原核表达及酶活测定表明该基因成功表达,表达产物在65 ℃时相对酶活性最高。【结论】本研究可为白腐菌纤维素酶大规模的工业化应用提供前期研究基础和理论依据。

【Objective】 Inonotus hispidus is a species of white rot fungi which mainly grow in the broadleaf tree of standing forest stock, and has medicinal efficacy, therefore with high application value and development value. Glycoside hydrolase can hydrolyze the cellulose into simple sugars which can be used to produce energy substances. 【Method】 In this study, we isolate and purified I. hispidus from Fraxinus mandshurica, and the fungus was preserved for long-term in the PDA cant medium. 【Result】 Total RNA of I. hispidus was extracted using TRIzol reagent. RNA was reversely transcribed to cDNA was analyzed and detected by AMV reverse transcription system, and then constructed cDNA library. The glycoside hydrolase family 5 gene positive sequence by NCBI BLAST, and the full-length of glycoside hydrolase family 5 gene was cloned by RACE, and named as IhGH 5-1 then registered in NCBI. All open reading frames of IhGH 5-1 were identifies by ORF Finder, and the amino acid sequence was deduced. The homologous sequences of glycoside hydrolase family 5 were detected from NCBI, and multiple sequence alignment was conducted by Clustal W. The maximum likelihood tree in WAG+G model was constructed by Mega 5.05. The secondary protein structure of IhGH5-1 was analyzed by PSIPRED server. The three dimensional model of IhGH5-1 was established using SWISS-MODEL, and 3d structure of IhGH5-1 was analyzed with VMD1.8.6. The prokaryotic expression primers were design, and the gene was cloned. The fragment was connected to the pQE-30 UA vector and transformed to E. coli JM109. Expression quantity inducible expression was detected using SDS-PAGE electrophoresis. The glycoside hydrolase activity was measured. Total extracted RNA of I. hispidus was measured by spectrophotometer (OD260/OD280=2.0,OD260/OD230>1.8). The cDNA library was successfully constructed and sequenced by Sangon Biotech Company. The 5‘ end sequence of the RACE was 770 bp, and 3‘ end sequence (containing PolyA sequence) was 1 562 bp. The whole length of the gene from the 3‘ end to the 5‘ end was 1 727 bp. GenBank accession number of the gene was KM368321. The amino acid sequence encoded by this gene contains 300 amino acids, the molecular weight is 31.226 55 kD, and the isoelectric point (pI) is 9.24. Domain structure analysis showed that IhGH5-1 has a conservative catalytic domain structure. The maximum likelihood tree showed that a closer relationship with the other glycoside hydrolase family 5 homologous was from fungus of Ascomycota, such as Thielavia terrestris and Chaetomium globosum. The three-dimensional comparison showed that three-dimensional structure of IhGH5-1 had seven alpha helixs, four beta foldings. It was found that the structure was similar with other fungal glycoside hydrolase family 5 protein spatial structures, and evolutionary relationships were consistent with the maximum likelihood tree analysis. The gene expression and enzymatic assays showed that the product of this gene had the highest relative activity at 65℃. 【Conclution】 The gene cloning and protein structural study of IhGH 5-1 would be a theoretical basis for industrial application of this enzyme.


全 文 :第 51 卷 第 2 期
2 0 1 5 年 2 月
林 业 科 学
SCIENTIA SILVAE SINICAE
Vol. 51,No. 2
Feb.,2 0 1 5
doi:10.11707 / j.1001-7488.20150220
收稿日期: 2013 - 11 - 22; 修回日期: 2014 - 08 - 27。
基金项目: 林业公益性行业科研专项项目(201004079) ; 中央高校基本科研业务费专项资金项目(DL13BA01)。
* 董爱荣为通讯作者。
粗毛纤孔菌糖苷水解酶 5 基因克隆及
蛋白质结构分析*
刘晓晗 王 峰 董爱荣 陈俏丽 刘立宏 零雅茗
王博文 丁晓霞 王世新
(东北林业大学林学院 哈尔滨 150040)
摘 要: 【目的】克隆得到粗毛纤孔菌糖苷水解酶 5 基因,并对该基因进行生物信息学分析、蛋白质原核表达和
酶活研究,为糖苷水解酶的利用提供依据。【方法】分离纯化粗毛纤孔菌,并于 PDA 斜面长期保存。应用 TRIzol 提
取粗毛纤孔菌总 RNA,通过 AMV 反转录系统将 RNA 反转录成 cDNA,构建 cDNA 文库; 应用 NCBI BLAST 分析并
检测糖苷水解酶基因家族 5 阳性序列,RACE 法克隆基因全长命名为 IhGH5-1 并提交 NCBI 注册; ORF-Finder 分析
IhGH5-1 基因开放阅读框,推导出氨基酸序列; 筛选 NCBI 登录的糖苷水解酶家族 5 同源序列,Clustal W 进行保守
结构域区段多序列比对; 应用 Mega 5. 05 选用 WAG + G 模型构建最大似然树; 应用 PSIPRED server 对 IhGH5-1 进
行 α 螺旋和 β 折叠的蛋白质二级结构分析,应用 SWISS-MODEL 对 IhGH5-1 进行三维建模,应用 VMD1. 8. 6 分析
IhGH5-1 三维结构; 设计原核表达引物并进行 PCR 扩增,将扩增得到的基因片段连接至 pQE-30 UA 载体并转入大
肠埃希菌 JM109 感受态细胞,诱导表达后通过 SDS-PAGE 电泳检测表达量; 测定糖苷水解酶活性并计算酶活。【结
果】TRIzol 提取的粗毛纤孔菌总 RNA 经分光光度计检验符合标准(OD260 /OD280 = 2. 0,OD260 /OD230 > 1. 8),cDNA 文
库成功构建并测序; RACE 法克隆得到 5序列长度为 770 bp,3序列长度为 1 562 bp 且含有 PolyA 的序列,5和 3序
列拼接得到基因全长序列长 1 727 bp,NCBI 注册号为 KM368321; ORF 分析得到 IhGH5-1 氨基酸序列含有 300 个
氨基酸,分子质量为31. 226 55 kD,等电点(pI)为 9. 24; 结构域分析表明 IhGH5-1 具有保守的催化结构域; 最大似
然树分析表明多数子囊菌糖苷水解酶家族 5 聚在一起,多数担子菌糖苷水解酶家族 5 聚在一起,粗毛纤孔菌
IhGH5-1 蛋白质与太瑞斯梭孢壳霉和球毛壳菌等子囊菌的糖苷水解酶亲缘关系更近; 蛋白质三维结构分析表明粗
毛纤孔菌 IhGH5-1 含有 7 个 α 螺旋、4 个 β 折叠,三维比对表明粗毛纤孔菌 IhGH5-1 三维结构与其他真菌糖苷水解
酶家族 5 蛋白空间结构相近,进化关系与最大似然树分析相符; 原核表达及酶活测定表明该基因成功表达,表达产
物在 65 ℃时相对酶活性最高。【结论】本研究可为白腐菌纤维素酶大规模的工业化应用提供前期研究基础和理论
依据。
关键词: 粗毛纤孔菌; 糖苷水解酶家族 5; 水曲柳; 木材白色腐朽
中图分类号: S718. 81 文献标识码: A 文章编号: 1001 - 7488(2015)02 - 0163 - 06
Gene Cloning and Protein Structural Studies of a Glycoside
Hydrolase Family 5 Enzyme Gene from Inonotus hispidus
Liu Xiaohan Wang Feng Dong Airong Chen Qiaoli Liu Lihong Ling Yaming
Wang Bowen Ding Xiaoxia Wang Shixin
(College of Forestry,Northeast Forestry University Harbin 150040)
Abstract: 【Objective】Inonotus hispidus is a species of white rot fungi which mainly grow in the broadleaf tree of
standing forest stock,and has medicinal efficacy,therefore with high application value and development value. Glycoside
hydrolase can hydrolyze the cellulose into simple sugars which can be used to produce energy substances. 【Method】In this
study,we isolate and purified I. hispidus from Fraxinus mandshurica,and the fungus was preserved for long-term in the
PDA cant medium. 【Result】Total RNA of I. hispidus was extracted using TRIzol reagent. RNA was reversely transcribed
to cDNA was analyzed and detected by AMV reverse transcription system,and then constructed cDNA library. The
glycoside hydrolase family 5 gene positive sequence by NCBI BLAST,and the full-length of glycoside hydrolase family 5
林 业 科 学 51 卷
gene was cloned by RACE,and named as IhGH5 - 1 then registered in NCBI. All open reading frames of IhGH5 - 1 were
identifies by ORF Finder,and the amino acid sequence was deduced. The homologous sequences of glycoside hydrolase
family 5 were detected from NCBI,and multiple sequence alignment was conducted by Clustal W. The maximum
likelihood tree in WAG + G model was constructed by Mega 5. 05. The secondary protein structure of IhGH5 - 1 was
analyzed by PSIPRED server. The three dimensional model of IhGH5 - 1 was established using SWISS-MODEL,and 3d
structure of IhGH5 - 1 was analyzed with VMD1. 8. 6. The prokaryotic expression primers were design,and the gene was
cloned. The fragment was connected to the pQE - 30 UA vector and transformed to E. coli JM109. Expression quantity
inducible expression was detected using SDS-PAGE electrophoresis. The glycoside hydrolase activity was measured. Total
extracted RNA of I. hispidus was measured by spectrophotometer (OD260 /OD280 = 2. 0,OD260 /OD230 > 1. 8) . The cDNA
library was successfully constructed and sequenced by Sangon Biotech Company. The 5 end sequence of the RACE was
770 bp,and 3 end sequence ( containing PolyA sequence) was 1 562 bp. The whole length of the gene from the 3‘ end
to the 5 ’end was 1 727 bp. GenBank accession number of the gene was KM368321. The amino acid sequence encoded
by this gene contains 300 amino acids,the molecular weight is 31. 226 55 kD,and the isoelectric point ( pI) is 9. 24.
Domain structure analysis showed that IhGH5 - 1 has a conservative catalytic domain structure. The maximum likelihood
tree showed that a closer relationship with the other glycoside hydrolase family 5 homologous was from fungus of
Ascomycota,such as Thielavia terrestris and Chaetomium globosum. The three-dimensional comparison showed that three-
dimensional structure of IhGH5 - 1 had seven alpha helixs,four beta foldings. It was found that the structure was similar
with other fungal glycoside hydrolase family 5 protein spatial structures,and evolutionary relationships were consistent with
the maximum likelihood tree analysis. The gene expression and enzymatic assays showed that the product of this gene had
the highest relative activity at 65℃ .【Conclution】The gene cloning and protein structural study of IhGH5 - 1 would be a
theoretical basis for industrial application of this enzyme.
Key words: Inonotus hispidus; glycoside hydrolase family 5; Fraxinus mandshurica; white rote
粗毛纤孔菌( Inonotus hispidus)是一种主要生长
在水 曲 柳 ( Fraxinus mandshurica )、榆 树 ( Ulmus
sp. )、桑树(Morus alba)等阔叶树活立木上的白腐
菌(Saddler,1982),子实体 1 年生,单生或覆瓦状叠
生,于夏季和秋季出现,晚秋后变黑。粗毛纤孔菌具
药用功效,应用和开发价值高。
纤维素是地球上分布较广且蕴藏量丰富的可再
生资源,充分利用纤维素可以缓解全球能源危机及
粮食短缺问题。碳水化合物降解酶能将纤维素水解
为单糖(单糖是进一步生产乙醇、丙酮和丁酮等化
合物的原料),对有效利用纤维素具有十分重要的
意义。碳水化合物降解酶分为糖苷水解酶(GHs)、
糖基转移酶(GTs)、多糖裂解酶(PLs)、碳水化合物
酯酶(CEs)、碳水化合物结合模块(CBMs) (Nicol et
al.,2012),其中,糖苷水解酶家族 GH5,6,7,8,9,
10,12,26,44,45,48,51,61 和 74 是纤维素酶
(Henrissat,1991)。本研究克隆到粗毛纤孔菌糖苷
水解酶家族 5 基因,并对该基因进行了生物信息学
分析、蛋白质原核表达和酶活研究,为下一步研究打
下基础。
1 材料与方法
1. 1 菌种采集及纯化培养 2008 年于哈尔滨林
业示范基地水曲柳活立木上采集木材腐朽菌子实
体。该子实体担子果平伏,覆瓦状叠生,木栓质。
菌盖金黄色,被粗毛,边缘钝。孔口表面金黄色,
多角形,每毫米 2 ~ 3 个(Rubini et al.,2010)。菌
管与孔口表面颜色相同,但明显比菌肉颜色浅。
担孢子椭圆形,表面光滑,金黄色,有明显厚壁。
ITS 序列系统发育树状图表明该粗毛纤孔菌与辐
射状纤孔菌亲缘关系较近。经过形态学和 ITS 区
序列 PCR 扩增后序列比对,鉴定为粗毛纤孔菌(郭
春宣等,2010),该菌种分离纯化后于 PDA 斜面长
期保存。
1. 2 cDNA 文库构建 RNA 提取试验前于纤维素
PDA 平板(1. 5%琼脂及 0. 5%羧甲基纤维素)诱导
培养菌苔备用。应用 TRIzol 提取总 RNA,DNase I
(RNase Free)(TaKaRa,Japan)消化后,采用 AMV 反
转录系统 ( Promega,Cat. No. A3500 ),以 Oligo
(dT) 18为引物反转录第 1 链 cDNA,随机引物合成第
2 链 cDNA(Robson et al.,1989)。双链 cDNA 加接
EcoR I 接头(400 ng·μL - 1 ),进行末端的磷酸化及
Xho I 酶切后连接至 pBlueScriptII 载体并转化至大
肠埃希菌(Escherichia coli)感受态细胞 DH5α。菌落
PCR 法筛选阳性克隆送上海生物工程公司测序。
1. 3 基因全长克隆 应用 NCBI BLASTN 2. 2. 16
461
第 2 期 刘晓晗等: 粗毛纤孔菌糖苷水解酶 5 基因克隆及蛋白质结构分析
在线比对测序结果。BLASTX /BLAST 分析,检测糖
苷水解酶家族 5 基因阳性序列。根据该序列设计
3RACE引物 ( In-GH5-5 R: 5-CCT TGC GGA TCC
CGT CGA TC-3)和 5RACE 引物( In-GH5-3F: 5-
TGA GTT CGG TGT ATG GAG -3),采用 Clontech 公
司的 Marathon RACE 试剂盒 ( Cat. No. 634913)进
行基因全长克隆,克隆产物分别送上海生物工程公
司测序,测序所得 3和 5序列拼接后命名为 IhGH5-
1,并提交 NCBI 注册。
1. 4 生物信息学分析及纤维素酶基因鉴定 ORF-
Finder( Open Reading Frame Finder of NCBI) 分析
IhGH5-1 基因开放阅读框,翻译氨基酸序列并进行
生物信息学分析(Wood et al.,1989)。筛选 NCBI 登
录的糖苷水解酶家族 5 同源序列,Clustal W 进行保
守结构域区段多序列比对。应用 Mega 5. 05 选用
WAG + G模型构建最大似然树(maximum likelihood
tree),自展检验(bootstrap test)重复次数为1 000。
1. 5 同源建模及结构分析 应用 PSIPRED server
对 IhGH5-1 进行 α 螺旋和 β 折叠的蛋白质二级结
构分析(Aggelis et al.,2002)。在二级结构分析的基
础上,应用 SWISS-MODEL 对 IhGH5-1 进行三维建
模,应用 VMD1. 8. 6 分析 IhGH5-1 三维结构。同源
三维结构比对,进一步修正后输出三维立体结构图。
1. 6 原核表达 应用 Primer Premier 5. 0 设计原核
表达所需引物 ( In-GH5-Ex-F: 5-CAA GCA GTA
GAG CGT ACC-3 和 In-GH5-Ex-R: 5- GTT GTC
GGA GAG ACG AGC T -3)并进行 PCR 扩增。分别
将扩增得到的 IhGH5-1 基因片段连接酶连接至
pQE-30 UA 载体,转化大肠埃希菌 JM109 感受态细
胞,LB 平板上筛选阳性重组子。阳性重组子经
IPTG(浓度 1 mmol·L - 1 )诱导 4 h。离心沉淀,生理
盐水洗涤后重悬,超声波破碎菌体,离心收集上清液
和沉淀,SDS-PAGE 电泳检测表达量(Muthezhilan et
al.,2007)。
1. 7 酶活测定 阳性 IhGH5-1 重组子采用 LB 液体
培养基发酵摇培,培养至指数期时添加 IPTG(终浓
度 1 mmol·L - 1)。发酵液 4 ℃离心 10 min,弃上清,
洗涤菌体并转至 50 mmol·L - 1磷酸缓冲液。冰浴超
声破碎,4 ℃离心 15 min 取上清液即为粗酶液。将
葡萄糖 80 ℃烘烤至恒重,配制母液,绘制标准曲线
(O’Leary et al.,2004 )。以羧甲基纤维素钠盐
(CMC-Na) 酶活性测定法,3,5 - 二硝基水杨酸
(DNS)显色测定不同温度下粗酶液 550 nm 吸光值,
并计算酶活。
2 结果与分析
2. 1 基因克隆 应用 TRIzol 提取粗毛纤孔菌总
RNA(图 1),经分光光度计检验符合标准 ( OD260 /
OD280 = 2. 0,OD260 /OD230 > 1. 8 )。RNA 反转录为
cDNA,构建 cDNA 文库并测序。经 BLASTN 对 EST
测序结果进行分析,得到一条糖苷水解酶家族 5 基
因同源序列片段,根据该序列设计引物 In-GH5-5R
和 In-GH5-3F。应用 RACE 法克隆得到 5序列长度
为 770 bp (图 1 泳道 3 ),3长度为 1 562 bp含有
PolyA 的序列(图 1 泳道 2)。5和 3序列拼接得到
基因全长序列长1 727 bp,提交 NCBI 注册,注册号
为 KM368321。经 ORF 分析得到 IhGH5-1 氨基酸序
列含有 300 个氨基酸,分子质量为31. 226 55 kD,等
电点(pI)为 9. 24。
图 1 RNA 及 IhGH5-1 基因全长克隆
Fig. 1 RNA and RACE of IhGH5-1 gene
M:DNA Marker DL2 000; 1: 粗毛纤孔菌 RNA RNA of I. hispidus ;
2: IhGH5-1 基因 3序列克隆 Clone 3 sequence of IhGH5-1 gene by
RACE; 3: IhGH5-1 基因 5序列克隆 Clone 5 sequence of IhGH5-1
gene by RACE.
2. 2 蛋白同源序列分析 筛选 NCBI 收录的真菌
IhGH5-1 同源序列 4 条(表 1),应用 Clustal W 程序
对同源序列保守结构域进行多序列比对。另下载
NCBI 登 录 的 担 子 菌 ( Basidomycota ) 和 子 囊 菌
(Ascomycota) IhGH5-1 同源序列 70 条,采用 PAUP
4. 0 和 Modetest 3. 06 依据赤池信息量准则 (Akaike
Information Criterion)选出 WAG + G 为进化的最适
模型构建最大似然树 (图 2B)。结构域分析表明
IhGH5-1 具有保守的催化结构域(Catalytic Domain)
(图 2A)。最大似然树分析表明多数子囊菌糖苷水
解酶家族 5 聚在一起,多数担子菌糖苷水解酶家族
5 聚在一起。但也有子囊菌糖苷水解酶家族 5 的系
统进化与菌物进化不完全一致,粗毛纤孔菌 IhGH5-
1 蛋白质与太瑞斯梭孢壳霉(Thielavia terrestris)和球
毛壳菌(Chaetomium globosum)等子囊菌的糖苷水解
酶亲缘关系更近。
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表 1 NCBI 登录的真菌纤维素酶同源序列
Tab. 1 Homologous sequences of fungal cellulase accessed on NCBI
物种
Species

Phylum
NCBI 序列号
NCBI accession No.
蛋白
Protein
E 值
E value
太瑞斯检验梭孢壳霉 Thielavia terrestris 子囊菌 Ascomycetes XP_003649276 GH5 6 - 102
球毛壳菌 Chaetomium globosum 子囊菌 Ascomycetes XP_001225331 GH5 1 - 75
Robillarda sp. 子囊菌 Ascomycetes P23044 纤维素酶 Cellulase 2 - 65
Ophiostoma piceae 子囊菌 Ascomycetes EPE05383 纤维素酶 Cellulase 7 - 57
图 2 IhGH5-1 同源序列比对及进化树
Fig. 2 Homologous sequence alignment and phylogenetic tree
A: IhGH5-1 及其同源序列保守结构域比对 The conserved domain of IhGH5-1 and homologous sequence alignment;
B: IhGH5-1 及其同源序列最大似然树 The maximum likelihood tree of IhGH5-1 and homologous sequence.
2. 3 蛋白质三维结构分析 以 PDB 注册结构
1h1nB 为模板进行同源建模后,以“Cartoon”模式,
从氮末端 (N-terminus)到碳末端 ( C-terminus)展示
粗毛纤孔菌 IhGH5-1 三维结构(图 3A)。粗毛纤孔
菌 IhGH5-1 含有 7 个 α 螺旋(图 3A A1 ~ A7),4 个
β 折叠(图 3A B1 ~ B4)。三维比对表明粗毛纤孔菌
IhGH5-1 三维结构与其他真菌糖苷水解酶家族 5 蛋
白空间结构相近(图 3B),进化关系与最大似然树分
析相符(图 3C)。
2. 4 IhGH5-1 原核表达及酶活测定 阳性 IhGH5-1
重组子经 IPTG(浓度 1 mmol·L - 1)诱导 4 h,样品经
超声波破碎后进行菌液离心,收集上清液。经 SDS-
PAGE 电泳检测,在约 30 kD 处检测到目的条带(图
4A),表明粗毛纤孔菌糖苷水解酶已成功表达。以
羧甲基纤维素钠盐(CMC-Na)酶活性测定法测定粗
酶液酶活,葡萄糖标准曲线符合线性相关(图 4B),
65 ℃时该酶相对活性最高(图 4C)。
3 讨论
纤维素是地球上含量最丰富、分布最广、合成量
最高的可再生碳水化合物资源,占植物干质量的1 /3
~ 1 /2,是植物细胞壁的主要成分 (Wilson,2011)。
由于纤维素是大分子有机物,短期内不易被降解,因
此,难以直接提高土壤肥力,影响田间耕作等农业生
产。长期以来,焚烧秸秆等农作物副产品,不但造成
了环境污染,同时也是有机资源的浪费(Guo et al.,
2008)。我国 20% 植物纤维素成为不可回收的垃
圾。纤维素酶可将纤维素这种宝贵的资源水解为葡
萄糖,进而生产乙醇、丁醇、丙酮等有机燃料和化工
原料( Petre et al.,1999),在能源、纺织、食品、洗涤
剂、饲料加工和造纸等领域的应用前景广阔 (李慧
蓉,2005)。纤维素酶是可以将纤维素降解为葡萄
糖的多组分酶系的总称,能水解天然纤维素的纤维
素酶都是复杂的多酶体系。纤维素酶依功能不同可
661
第 2 期 刘晓晗等: 粗毛纤孔菌糖苷水解酶 5 基因克隆及蛋白质结构分析
图 3 真菌糖苷水解酶家族 5 蛋白空间结构
Fig. 3 The protein spatial structure of fungal glycoside hydrolase family 5
A: IhGH5-1 三维结构 Three-dimensional structure of IhGH5-1; B: 真菌糖苷水解酶家族 5 蛋白空间结构比对 The protein structure alignment of
fungal glycoside hydrolase family 5; C: 真菌糖苷水解酶家族 5 蛋白进化分析 The phylogenetic analysis of fungal glycoside hydrolase family 5.
图 4 SDS-PAGE 电泳及酶活测定
Fig. 4 Electrophoresis and enzymatic assays of SDS-PAGE
A: SDS-PAGE 电泳 SDS-PAGE electrophoresis; B: 葡萄糖标准曲线 Standard curve of glucose; C: 不同温度条件下相对酶活 Relative activity under
different temperature conditions.
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林 业 科 学 51 卷
分为 3 大 类: 葡 萄 糖 内 切 酶 ( endo-1, 4-β-D,
glucanase,E. C 3. 2. 1. 4,来自真菌简称 EG,来自细
菌简 称 Len )、葡 萄 糖 外 切 酶 ( exo-1, 4-β-D,
glucanase,E. C 3. 2. 1. 91)和 β -葡萄糖苷酶(β-1,
4-glucanase. E. C 3. 2. 1. 21,简称 BG)。
纤维素酶在能源、食品、饲料加、纺织、洗涤剂、
造纸等众多领域有着十分广阔的应用前景,此外利
用生物质纤维素,制取乙醇燃料也是目前的研究热
点,因此,筛选和驯化出能生产高活性纤维素酶的菌
株势在必行。由于白腐菌既可以降解木质素又可以
降解纤维素,因此在木质纤维素类物质降解生产中
具有重要地位。目前,已经从黄孢原毛平革菌
( Phanerochaete chrysosporium )、侧 耳 菌 ( Pleurotus
sp. )等白腐菌中得到了能够降解纤维素的纤维素酶
( Ichiro et al.,2012);本研究从另一种白腐菌———粗
毛纤孔菌中克隆到了糖苷水解酶家族 5 基因,并进
行了蛋白质结构、原核表达和活性分析,为进一步研
究以便大规模的工业化应用做了铺垫。
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