Characterization of a laccase from a wood-feeding termite,Coptotermes formosanus

• 来源期刊: 中国昆虫科学（英文版）
• 关键词: biological pretreatment Coptotermes formosanus heterogeneous expression laccase lignin modification termite
• 年，卷（期）: 2018,（2）
• 页码范围: 251-258
• 页数: 8页
• 语种: 英文
• DOI: 10.1111/1744-7917.12415

摘要

Coptotermes formosanus Shiraki is a wood-feeding termite which secretes a series of lignolytic and cellulolytic enzymes for woody biomass degradation.However,the lignin modification mechanism in the termite is largely elusive,and the characteristics of most lignolytic enzymes in termites remain unknown.In this study,a laccase gene lacl from C formosanus was heterogeneously expressed in insect Sf9 cells.The purified Lac I showed strong activities toward hydroquinone (305 mU/mg) and 2,6-dimethoxyphenol (2.9 mU/mg) with low Km values,but not veratryl alcohol or 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid).Lac 1 could function well from pH 4.5 to 7.5,and its activity was significantly inhibited by H2O2 at above 4.85 mmol/L (P ＜ 0.01).In addition,the lacl gene was found to be mainly expressed in the salivary glands and foregut of C.formosanus,and seldom in the midgut or hindgnt.These findings suggested that Lacl is a phenol-oxidizing laccase like RflacA and RflacB from termite Reticulitermesflavipes,except that Lacl was found to be more efficient in phenol oxidation,and it did not require H2O2 for its function.It is suspected that this kind of termite laccase might only be able to directly oxidize low redox-potential substrates,and the high redox-potential groups in lignin might be oxidized by other enzymes in the termite or by using the Fenton reaction.