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Structural basis of carbohydrate binding in domain C of a type I pullulanase from Paenibacillus barengoltzii
Author(s) -
Huang Ping,
Wu Shiwang,
Yang Shaoqing,
Yan Qiaojuan,
Jiang Zhengqiang
Publication year - 2020
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.374
H-Index - 138
ISSN - 2059-7983
DOI - 10.1107/s205979832000409x
Subject(s) - pullulanase , carbohydrate binding module , glycoside hydrolase , chemistry , stereochemistry , binding site , pullulan , glycosidic bond , hydrolase , enzyme , binding domain , biochemistry , polysaccharide
Pullulanase (EC 3.2.1.41) is a well known starch‐debranching enzyme that catalyzes the cleavage of α‐1,6‐glycosidic linkages in α‐glucans such as starch and pullulan. Crystal structures of a type I pullulanase from Paenibacillus barengoltzii ( Pb PulA) and of Pb PulA in complex with maltopentaose (G5), maltohexaose (G6)/α‐cyclodextrin (α‐CD) and β‐cyclodextrin (β‐CD) were determined in order to better understand substrate binding to this enzyme. Pb PulA belongs to glycoside hydrolase (GH) family 13 subfamily 14 and is composed of three domains (CBM48, A and C). Three carbohydrate‐binding sites identified in Pb PulA were located in CBM48, near the active site and in domain C, respectively. The binding site in CBM48 was specific for β‐CD, while that in domain C has not been reported for other pullulanases. The domain C binding site had higher affinity for α‐CD than for G6; a small motif (FGGEH) seemed to be one of the major determinants for carbohydrate binding in this domain. Structure‐based mutations of several surface‐exposed aromatic residues in CBM48 and domain C had a debilitating effect on the activity of the enzyme. These results suggest that both CBM48 and domain C play a role in binding substrates. The crystal forms described contribute to the understanding of pullulanase domain–carbohydrate interactions.