الفهرس 
الفصل الاولOnly 14 pages are availabe for public view
 |  | from | 92 |  |  |
| | | from | 92 | | |
Abstract
Glycosidases or glycoside hydrolases (EC 3.2.1.) are hydrolytic enzymes, which catalyze the cleavage of the glycosidic bond of disaccharides, oligosaccharides, polysaccharides and glycoconjugates [1]. They contain several important enzymes such as α-amylase (EC 3.2.1.1), α-glucosidase (EC 3.2.1.20), β-glucosidase (EC 3.2.1.21), isomaltase (EC 3.2.1.10), sucrase (EC 3.2.1.48), β-glucuronidase (EC 3.2.1.31) and trehalase (EC 3.2.1.28). These enzymes are essential in the digestion, metabolism and processing of carbohydrates [2]. Glycosidases (EC 3.2.1.), enzymes that hydrolyze O- and S-glycosyl residues, are involved in the biosynthesis of the oligosaccharide Chains and quality control mechanisms in the endoplasmic reticulum (ER) of the N-linked glycoproteins [3]. Enzymes degrading starch generally classified into two groups, endo-acting enzymes (endohydralases) and exo-acting enzymes (exohydralases) [4]. Endo acting enzyme like α -amylase (α -1, 4glucan-4-glucanohydralse; EC 3.2.1.1), which randomly hydrolyses linkages between starch polymer chain, leading to the generation of linear and branched oligosaccharides. Most starch-hydrolyzing enzymes is a member of the α-amylase family having a characteristic catalytic (β/α)8 barrel domain. α– glucosidase (EC 3.2.1.20) attacks α -1, 4 linkages of oligosaccharides and releases glucose by retentive a α- numeric configuration. Exo-acting starch hydrolases such as β-amylase, glucoamylase, α-glucosidase and isoamylase attack the substrate from the non-reducing end producing oligosaccharides. βamylase (EC3.2.1.2), also mentioned to as α-1, 4-D–glycan maltohydrolase or saccharogen amylase which hydrolyses α-1, 4-glucosidic linkages of the starch chain to liberate successive maltose units from the non-reducing end that giving β -maltose units by an reverse of configuration.