title: A 24.7-kDa copper-containing oxidase, secreted by Thermobifida fusca, significantly increasing the xylanase/cellulase-catalyzed hydrolysis of sugarcane bagasse.
abstract: Thermobifida fusca is a moderately thermophilic soil bacterium belonging to Actinobacteria. It has been known for its capability to degrade plant cell wall polymers except lignin and pectin. To know whether it can produce enzymes to facilitate lignin degradation, the extracellular proteins bound to sugarcane bagasse were harvested and identified by liquid chromatography tandem mass spectrometry. Among the identified proteins, a putative copper-containing polyphenol oxidase of 241 amino acids, encoded by the locus Tfu_1114, was thought to presumably play a role in lignin degradation. This protein (Tfu1114) was thus expressed in E. coli and characterized. Similarly to common laccases, Tfu1114 is able to catalyze the oxidation reaction of phenolic and nonphenolic lignin related compounds such as 2,6-dimethoxyphenol and veratryl alcohol. More interestingly, it can significantly enhance the enzymatic hydrolysis of bagasse by xylanase and cellulase. Tfu1114 is stable against heat, with a half-life of 4.7 h at 90 °C, and organic solvents. It is sensitive to ethylenediaminetetraacetic acid and reducing agents but resistant to sodium azide, a potent inhibitor of laccases. Atomic absorption spectroscopy indicated that the ratio of copper to the protein monomer is 1, instead of 4, a feature of classical laccases. All these data suggest that Tfu1114 is a novel oxidase with laccase-like activity, potentially useful in biotechnology application.
authors: Graduate Institute of Biotechnology, National Chung Hsing University, 250 Kuo-Kuang Rd, Taichung, Taiwan, 40227, Republic of China.
authors: Cheng-Yu
authors: CY
authors: Chen
authors: Zhi-Shen
authors: ZS
authors: Hsieh
authors: Jatuporn
authors: J
authors: Cheepudom
authors: Chao-Hsun
authors: CH
authors: Yang
authors: Menghsiao
authors: M
authors: Meng
mesh_terms: D000192:Actinomycetales / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D004156:Catechol Oxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002480:Cellulase / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry*; D004795:Enzyme Stability; D006868:Hydrolysis; D007220:Industrial Waste / Q000032:analysis; D007700:Kinetics; D008031:Lignin / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D031786:Saccharum / Q000737:chemistry* / Q000382:microbiology; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D007220:Industrial Waste; D002482:Cellulose; D008031:Lignin; C027433:bagasse; D004156:Catechol Oxidase; D002480:Cellulase; D043364:Endo-1,4-beta Xylanases