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Structure and function of the type III pullulan hydrolase from Thermococcus kodakarensis

DOI: 10.1107/S2059798318001754 DOI Help

Authors: Jingxu Guo (University College London) , Alun Coker (University College London) , Steve P. Wood (University College London) , Jonathan Cooper (University College London; Birkbeck, University of London) , Ronan M. Keegan (CCP4, Research Complex at Harwell; Science and Technology Facilities Council; University of Liverpool) , Nasir Ahmad (University of the Punjab) , Majida Atta Muhammad (University of the Punjab) , Naeem Rashid (University of the Punjab) , Muhummad Akhtar (University of the Punjab)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Crystallographica Section D Structural Biology , VOL 74 , PAGES 305 - 314

State: Published (Approved)
Published: April 2018
Diamond Proposal Number(s): 12342

Abstract: Pullulan-hydrolysing enzymes, more commonly known as debranching enzymes for starch and other polysaccharides, are of great interest and have been widely used in the starch-saccharification industry. Type III pullulan hydrolase from Thermococcus kodakarensis (TK-PUL) possesses both pullulanase and α-amylase activities. Until now, only two enzymes in this class, which are capable of hydrolysing both α-1,4- and α-1,6-glycosidic bonds in pullulan to produce a mixture of maltose, panose and maltotriose, have been described. TK-PUL shows highest activity in the temperature range 95–100°C and has a pH optimum in the range 3.5–4.2. Its unique ability to hydrolyse maltotriose into maltose and glucose has not been reported for other homologous enzymes. The crystal structure of TK-PUL has been determined at a resolution of 2.8 Å and represents the first analysis of a type III pullulan hydrolyse. The structure reveals that the last part of the N-terminal domain and the C-terminal domain are significantly different from homologous structures. In addition, the loop regions at the active-site end of the central catalytic domain are quite different. The enzyme has a well defined calcium-binding site and possesses a rare vicinal disulfide bridge. The thermostability of TK-PUL and its homologues may be attributable to several factors, including the increased content of salt bridges, helical segments, Pro, Arg and Tyr residues and the decreased content of serine.

Journal Keywords: pullulan hydrolase; Thermococcus kodakarensis; protein crystallography; structural biology

Subject Areas: Biology and Bio-materials


Instruments: I03-Macromolecular Crystallography

Added On: 11/04/2018 09:43

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