Human α-L-iduronidase uses its own N-glycan as a substrate-binding and catalytic module

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 36; pp. 14628 - 14633
• Main Authors: Maita, Nobuo, Tsukimura, Takahiro, Taniguchi, Takako, Saito, Seiji, Ohno, Kazuki, Taniguchi, Hisaaki, Sakuraba, Hitoshi
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 03.09.2013; National Acad Sciences
• Subjects: Amino Acid Sequence; Atomic interactions; Atoms; Binding Sites; Biocatalysis; Biological Sciences; Circular Dichroism; Crystal structure; Crystallography, X-Ray; Dermatan Sulfate - metabolism; Electrophoresis, Polyacrylamide Gel; Enzyme activity; Enzymes; Heparitin Sulfate - metabolism; Humans; Iduronidase - chemistry; Iduronidase - genetics; Iduronidase - metabolism; Kinetics; Mannose - chemistry; Mannose - metabolism; Models, Molecular; Molecular Sequence Data; Mucopolysaccharidosis I - enzymology; Mucopolysaccharidosis I - metabolism; Mutation; Oligosaccharides; Polysaccharides; Polysaccharides - chemistry; Polysaccharides - metabolism; Protein Binding; Protein Structure, Tertiary; Research universities; Sequence Homology, Amino Acid; Substrate Specificity; Sugars; Sulfates; X-ray crystallography; glycoside hydrolase family 39; N-linked glycan
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1306939110

N-glycosylation is a major posttranslational modification that endows proteins with various functions. It is established that N-glycans are essential for the correct folding and stability of some enzymes; however, the actual effects of N-glycans on their activities are poorly understood. Here, we show that human α-L-iduronidase (hlDUA), of which a dysfunction causes accumulation of dermatan/heparan sulfate leading to mucopolysaccharidosis type I, uses its own N-glycan as a substrate binding and catalytic module. Structural analysis revealed that the mannose residue of the N-glycan attached to N372 constituted a part of the substrate-binding pocket and interacted directly with a substrate. A deglycosylation study showed that enzyme activity was highly correlated with the N-glycan attached to N372. The kinetics of native and deglycosylated hIDUA suggested that the N-glycan is also involved in catalytic processes. Our study demonstrates a previously unrecognized function of N-glycans.