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|Title:||Family 39 a-L-iduronidases and b-D-xylosidases react through similar glycosyl-enzyme intermediates: Identification of the human iduronidase nucleophile|
|Citation:||Biochemistry, 2003; 42(26):8054-8065|
|Publisher:||Amer Chemical Soc|
|Abstract:||The inclusion of both beta-D-xylosidases and alpha-L-iduronidases within the same sequence-related family (family 39), despite the considerable difference in substrate structures and poor sequence conservation around the putative nucleophile, raises concerns about whether a common mechanism is followed by the two enzymes. A novel anchimeric assistance mechanism for iduronidases involving a lactone intermediate is one possibility. NMR analysis of the methanolysis reaction catalyzed by human alpha-L-iduronidase reveals that, as with the beta-D-xylosidases, alpha-L-iduronidase is a retaining glycosidase. Using two different mechanism-based inactivators, 5-fluoro-alpha-L-iduronyl fluoride and 2-deoxy-2-fluoro-alpha-L-iduronyl fluoride, the active site nucleophile in the human alpha-L-iduronidase was identified as Glu299 within the (295)IYNDEAD(301) sequence. The equivalent, though loosely predicted, glutamic acid was identified as the nucleophile in the family 39 beta-D-xylosidase from Bacillus sp. [Vocadlo, D., et al. (1998) Biochem. J. 335, 449-455]; thus, a common mechanism involving a covalent glycosyl-enzyme intermediate that adopts the rather uncommon (2,5)B conformation is predicted.|
Amino Acid Sequence
Sequence Homology, Amino Acid
Molecular Sequence Data
|Appears in Collections:||Aurora harvest|
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