A motif rich in charged residues determines product specificity in isomaltulose synthase

FEBS Letters

Swaminathan, Kunchithapadam¹  Zhang, Lian-Hui²  Zhang, Daohai²  Li, Nan¹ 

[1]Laboratory of Crystallography, Institute of Molecular and Cell Biology, 30 Medical Drive, The National University of Singapore, Singapore 117609, Singapore

[2]Laboratory of Biosignals and Bioengineering, Institute of Molecular and Cell Biology, The National University of Singapore, Singapore 117609, Singapore

关键词: Isomaltulose synthase;    Motif;    Sucrose isomerization;    Isomaltulose;    Trehalulose;   

DOI  :  10.1016/S0014-5793(02)03835-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Isomaltulose synthase (PalI) catalyzes hydrolysis of sucrose and formation of α-1,6 and α-1,1 bonds to produce isomaltulose (α-D-glucosylpyranosyl-1,6-D-fructofranose) and small amount of trehalulose (α-D-glucosylpyranosyl-1,1-D-fructofranose). A potential isomaltulose synthase-specific motif (³²⁵RLDRD³²⁹), that contains a ‘DxD’ motif conserved in many glycosyltransferases, was identified based on sequence comparison with reference to the secondary structural features of PalI and homologs. Site-directed mutagenesis analysis of the motif showed that the four charged amino acid residues (Arg³²⁵, Arg³²⁸, Asp³²⁷ and Asp³²⁹) influence the enzyme kinetics and determine the product specificity. Mutation of these four residues increased trehalulose formation by 17–61% and decreased isomaltulose by 26–67%. We conclude that the ‘RLDRD’ motif controls the product specificity of PalI.

【 授权许可】

Unknown