Please use this identifier to cite or link to this item: https://doi.org/10.1074/jbc.M302616200
Title: Isomaltulose synthase (PalI) of Klebsiella sp. LX3: Crystal structure and implication of mechanism
Authors: Zhang, D.
Li, N.
Lok, S.-M.
Zhang, L.-H.
Swaminathan, K. 
Issue Date: 12-Sep-2003
Source: Zhang, D., Li, N., Lok, S.-M., Zhang, L.-H., Swaminathan, K. (2003-09-12). Isomaltulose synthase (PalI) of Klebsiella sp. LX3: Crystal structure and implication of mechanism. Journal of Biological Chemistry 278 (37) : 35428-35434. ScholarBank@NUS Repository. https://doi.org/10.1074/jbc.M302616200
Abstract: Isomaltulose synthase from Klebsiella sp. LX3 (PalI, EC 5.4.99.11) catalyzes the isomerization of sucrose to produce isomaltulose (α-D-glucosylpyranosyl-1,6-D-fructofuranose) and trehalulose (α-D-glucosylpyranosyl-1,1-D-fructofuranose). The PalI structure, solved at 2.2-Å resolution with an R-factor of 19.4% and Rfree of 24.2%, consists of three domains: an N-terminal catalytic (β/α) 8 domain, a subdomain between Nβ3 and Nα3, and a C-terminal domain having seven β-strands. The active site architecture of PalI is identical to that of other glycoside hydrolase family 13 members, suggesting a similar mechanism in substrate binding and hydrolysis. However, a unique RLDRD motif in the proximity of the active site has been identified and shown biochemically to be responsible for sucrose isomerization. A two-step reaction mechanism for hydrolysis and isomerization, which occurs in the same pocket is proposed based on both the structural and biochemical data. Selected C-terminal truncations have been shown to reduce and even abolish the enzyme activity, consistent with the predicted role of the C-terminal residues in the maintenance of enzyme conformation and active site topology.
Source Title: Journal of Biological Chemistry
URI: http://scholarbank.nus.edu.sg/handle/10635/100988
ISSN: 00219258
DOI: 10.1074/jbc.M302616200
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