Unusual Role of the 3-OH Group of Oligosaccharide Substrates in the Mechanism ofBacillus1,3-1,4-β-glucanase

Autor:	Mireia Abel, Antoni Segade, Antoni Planas, Juan Nieto
Rok vydání:	2003
Předmět:	chemistry.chemical_classification Reaction mechanism Hydrogen bond Stereochemistry Substituent Substrate (chemistry) Oligosaccharide Biochemistry Catalysis chemistry.chemical_compound chemistry Non-covalent interactions Tetrasaccharide Biotechnology
Zdroj:	Biocatalysis and Biotransformation. 21:223-231
ISSN:	1029-2446 1024-2422
DOI:	10.1080/10242420310001618500
Popis:	In the mechanism of retaining β-glycosidases, the 2-hydroxyl group of the substrate in the monosaccharyl unit involved in catalysis (subsite -1) is beleived to play an important role through hydrogen bonding interactions with protein residues that are optimized at the transition state. Commonly, removal of the 2-OH group of the substrate results in a 10–12 kcal·mol-1 transition state destabilization. However, this effect seems not to be general as reported here for Bacillus 1,3-1,4-β-glucanase, a family 16 retaining endo-glycosidase. A p-nitrophenol 2-deosxy tetrasaccharide substrate was synthesized to probe the involvement of the 2-OH group in catalysis. Comparative kinetics with wild-type and subsite +1 mutants show that the 2-deoxy analog is a better substrate than the corresponding 2-hydroxy substrate. It is tentatively proposed that the 2-deoxy analog adopts a different conformation upon binding that compensates for the lack of the 2-OH substituent.
Databáze:	OpenAIRE
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