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Galactosides
A galactoside is a glycoside containing galactose. The H of the OH group on carbon-1 of galactose is replaced by an organic moiety. Depending on whether the glycosidic bond lies "above" or "below" the plane of the galactose molecule, galactosides are classified as α-galactosides or β-galactosides. A β-galactoside is a type of galactoside in which the glycosidic bond lies above the plane of the galactose Galactose (, '' galacto-'' + ''-ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molecu ... residue. The most commonly recognized and used β-galactoside in biochemistry is lactose. However, other chemicals, such as ONPG, are known, but these are typically synthesized for biochemical assays. Galactosides play significant roles in metabolic processes of many organisms and are hydrolyzed by a class of enzymes called g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta-galactosidase
β-Galactosidase (EC 3.2.1.23, lactase, beta-gal or β-gal; systematic name β-D-galactoside galactohydrolase), is a glycoside hydrolase enzyme that catalyzes hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides. β-Galactosides include carbohydrates containing galactose where the glycosidic bond lies above the galactose molecule. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins. Function β-Galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but with much lower efficiency. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In '' E. coli'', the ''lacZ'' gene is the structural gene for β-galactosidase; which is present as part of the inducible system ''lac'' operon which is activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha-galactosidase
α-Galactosidase ( EC 3.2.1.22, α-GAL, α-GAL A; systematic name α-D-galactoside galactohydrolase) is a glycoside hydrolase enzyme that catalyses the following reaction: : Hydrolysis of terminal, non-reducing α-D-galactose residues in α-D-galactosides, including galactose oligosaccharides, galactomannans and galactolipids It catalyzes many catabolic processes, including cleavage of glycoproteins, glycolipids, and polysaccharides. The enzyme is encoded by the ''GLA'' gene. Two recombinant forms of human α-galactosidase are called agalsidase α (INN) and agalsidase β (INN). A mold-derived form is the primary ingredient in gas relief supplements. Function This enzyme is a homodimeric glycoprotein that hydrolyses the terminal α-galactosyl moieties from glycolipids and glycoproteins. It predominantly hydrolyzes ceramide trihexoside, and it can catalyze the hydrolysis of melibiose into galactose and glucose. Reaction mechanism Disease relevance Fabry disease ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. Many such plant glycosides are used as medications. Several species of ''Heliconius'' butterfly are capable of incorporating these plant compounds as a form of chemical defense against predators. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body. In formal terms, a glycoside is any molecule in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond. Glycosides can be linked by an O- (an ''O-glycoside''), N- (a ''glycosylamine''), S-(a ''thioglycoside''), or C- (a '' C-glycoside'') glycosidic bond. According to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactose
Galactose (, '' galacto-'' + '' -ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molecule linked with a glucose molecule forms a lactose molecule. Galactan is a polymeric form of galactose found in hemicellulose, and forming the core of the galactans, a class of natural polymeric carbohydrates. D-Galactose is also known as brain sugar since it is a component of glycoproteins (oligosaccharide-protein compounds) found in Nerve tissue, nerve tissue. Etymology The word ''galactose'' was coined by Charles Weissman in the mid-19th century and is derived from Greek ''galaktos'' (of milk) and the generic chemical suffix for sugars ''-ose''. The etymology is comparable to that of the word '' lactose'' in that both contain roots meaning "milk sugar". Lactose is a disaccharide of galactose plus glucose. Structure and isomerism Gal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycosidic Bond
A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside. The term 'glycoside' is now extended to also cover compounds with bonds formed between hemiacetal (or hemiketal) groups of sugars and several chemical groups other than hydroxyls, such as -SR (thioglycosides), -SeR (selenoglycosides), -NR1R2 (N-glycosides), or even -CR1R2R3 (C-glycosides). Particularly in naturally occurring glycosides, the compound ROH from which the carbohydrate residue has been removed is often termed the aglycone, and the carbohydrate residue itself is sometimes referred to as the 'glycone'. S-, N-, C-, and O-glycosidic bonds Glycosidi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactose
Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix '' -ose'' used to name sugars. The compound is a white, water-soluble, non-hygroscopic solid with a mildly sweet taste. It is used in the food industry. Structure and reactions Lactose is a disaccharide derived from the condensation of galactose and glucose, which form a β-1→4 glycosidic linkage. Its systematic name is β-D-galactopyranosyl-(1→4)-D-glucose. The glucose can be in either the α-pyranose form or the β-pyranose form, whereas the galactose can only have the β-pyranose form: hence α-lactose and β-lactose refer to the anomeric form of the glucopyranose ring alone. Detection reactions for lactose are the Woehlk- and Fearon's test. Both can be easily used in school experiments to visualise the different lactose content o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
