Characterization and homology modelling of a novel multi-modular and multi-functional Paenibacillus mucilaginosus glycoside hydrolase
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Glycoside hydrolases, particularly cellulases, xylanases and mannanases, are essential for the depolymerisation of lignocellulosic substrates in various industrial bio-processes. In the present study, a novel glycoside hydrolase from Paenibacillus mucilaginosus (PmGH) was expressed in E. coli, purified and characterised. Functional analysis indicated that PmGH is a 130 kDa thermophilic multi-modular and multi-functional enzyme, comprising a GH5, a GH6 and two CBM3 domains and exhibiting cellulase, mannanase and xylanase activities. The enzyme displayed optimum hydrolytic activities at pH 6 and 60 °C and moderate thermostability. Homology modelling of the full-length protein highlighted the structural and functional novelty of native PmGH, with no close structural homologs identified. However, homology modelling of the individual GH5, GH6 and the two CBM3 domains yielded excellent models based on related structures from the Protein Data Bank. The catalytic GH5 and GH6 domains displayed a (β/α)8 and a distorted seven stranded (β/α) fold, respectively. The distinct homology at the domain level but low homology of the full-length protein suggests that this protein evolved by exogenous gene acquisition and recombination.
KeywordsMulti-modular Multi-functional Thermophilic enzyme Paenibacillus mucilaginosus
Carbohydrate Active enZYme database
Carbohydrate binding module
Global Model Quality Estimation
Immobilized Metal Affinity Chromatography
Paenibacillus mucilaginosus glycoside hydrolase
Sodium dodecyl sulphate–polyacrylamide gel electrophoresis
The authors gratefully acknowledge the National Research Foundation for project funding. NLM wishes to thank the NRF for the Innovation Doctoral Scholarship.
Compliance with ethical standards
Conflict of interest
The authors declare they have no conflict of interest.
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