title: Type-dependent action modes ofTtAA9E andTaAA9A acting on cellulose and differently pretreated lignocellulosic substrates.
abstract: BACKGROUND
  Lytic polysaccharide monooxygenase (LPMO) is a group of recently identified proteins that catalyze oxidative cleavage of the glycosidic linkages of cellulose and other polysaccharides. By utilizing the oxidative mode of action, LPMOs are able to enhance the efficiency of cellulase in the hydrolysis of cellulose. Particularly, auxiliary activity family 9 (AA9) is a group of fungal LPMOs that show a type-dependent regioselectivity on cellulose in which Types 1, 2, and 3 hydroxylate at C1, C4, and C1 and C4 positions, respectively. In this study, we investigated comparative characteristics ofTtAA9E fromThielavia terrestrisbelonging to Type 1 andTaAA9A fromThermoascus aurantiacusbelonging to Type 3 on cellulose and pretreated lignocellulose.
  
  
  RESULTS
  From product analysis,TtAA9E dominantly generated oligosaccharides with an aldonic acid form, which is an evidence of C1 oxidation, whileTaAA9A generated oligosaccharides with both aldonic acid and 4-ketoaldose forms, which is evidence of C1 and C4 oxidations, respectively. For hydrolysis of cellulose (Avicel) by cellulase, higher synergism was observed forTtAA9E than forTaAA9A. For hydrolysis of pretreated lignocellulose using rice straw, synergistic behaviors ofTtAA9E andTaAA9A were different depending on the pretreatment of rice straw. Specifically, on acid-pretreated rice straw,TtAA9E showed a higher synergism thanTaAA9A while on alkali-pretreated rice straw,TaAA9A showed a higher synergism thanTtAA9E.
  
  
  CONCLUSIONS
  We show type-dependent action modes ofTtAA9E andTaAA9A for cellulose oxidation together with substrate-dependent synergistic hydrolysis of cellulosic substrates. The results obtained from this study indicate the different behaviors of AA9s on cellulose and pretreated lignocellulose, suggesting a selection of AA9 proteins specific to substrates is required for industrial utilization.
authors.affiliation: Department of Biotechnology, Korea University, Graduate School, Seoul, 02841 South Korea.
authors.forename: In Jung
authors.initials: IJ
authors.lastname: Kim
authors.affiliation: Graduate School of Analytical Science & Technology and Asia-Pacific Glycomics Reference Site, Chungnam National University, Daejeon, 34134 South Korea.
authors.forename: Nari
authors.initials: N
authors.lastname: Seo
authors.affiliation: Graduate School of Analytical Science & Technology and Asia-Pacific Glycomics Reference Site, Chungnam National University, Daejeon, 34134 South Korea.
authors.forename: Hyun Joo
authors.initials: HJ
authors.lastname: An
authors.affiliation: Department of Food and Nutrition, Chungnam National University, Daejeon, 34134 South Korea.
authors.forename: Jae-Han
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Novozymes, Davis, CA 95618 USA.
authors.forename: Paul V
authors.initials: PV
authors.lastname: Harris
authors.affiliation: Department of Biotechnology, Korea University, Graduate School, Seoul, 02841 South Korea.
authors.forename: Kyoung Heon
authors.identifier: 0000-0003-4600-8668
authors.initials: KH
authors.lastname: Kim
keywords: Auxiliary activity family 9; Cellulose hydrolysis; Cellulose oxidation; Glycoside hydrolase family 61; Lytic polysaccharide monooxygenase; Synergism