Nutrition Guide

In enzymology, a xyloglucan-specific endo-beta-1,4-glucanase (EC 3.2.1.151) is an enzyme that catalyzes the chemical reaction
xyloglucan + H2O xyloglucan oligosaccharides

Thus, the two substrates of this enzyme are xyloglucan and H2O, whereas its product is xyloglucan oligosaccharides.

This enzyme belongs to the family of hydrolases, specifically those glycosidases that hydrolyse O- and S-glycosyl compounds. The systematic name of this enzyme class is [(1->6)-alpha-D-xylo]-(1->4)-beta-D-glucan glucanohydrolase. Other names in common use include XEG, xyloglucan endo-beta-1,4-glucanase, xyloglucanase, xyloglucanendohydrolase, XH, and 1,4-beta-D-glucan glucanohydrolase.

Xylanase (EC 3.2.1.8) is the name given to a class of enzymes which degrade the linear polysaccharide beta-1,4-xylan into xylose[1], thus breaking down hemicellulose, which is a major component of the cell wall of plants.

As such, it plays a major role in the digestive system of herbivorous micro-organisms (mammals, conversely, do not produce xylanase). Additionally, xylanases are present in fungi for the degradation of plant matter into usable nutrients.

Commercial applications for xylanase include the chlorine-free bleaching of wood pulp prior to the papermaking process, and the increased digestibility of silage (in this aspect, it is also used for fermentative composting). (Gulzar, Production and partial purification of Xylanase fromTrichoderma longibrachiatum. Published in international conference on biotechnology and neurosciences. CUSAT , 2004.P33).

Additionally, it is the key ingredient in the dough conditioners s500 and us500 manufactured by Puratos. These enzymes are used to improve the dough’s workability and absorption of water. [2]

In the future, xylanase may be used for the production of biofuel from unusable plant material [3].

The molecular weight of AT was found to be 218 kDa by gel filtration chromatography. AT is a glycoprotein. It has 86% carbohydrate content. It has been reported that the maturation of AT is a stepwise process beginning with a carbohydrate-free 41 kDa protein; this form is then core-glycosylated in the endoplasmic reticulum to form a 76 kDa glycol-protein. In Golgi bodies, the protein is further glycosylated yielding a 180 kDa form, which ultimately attains a maturity in vacuoles, where its molecular weight becomes around 220 kDa . The 41 kDa carbohydrate free protein moiety of the enzyme was obtained by Endoglycosidase H treatment of purified AT, resulted after sodium dodecyl sulfate gel electrophoresis27. AT exhibited an apparent Km for trehalose of about 4.7 mM at pH 4.5. The gene responsible for AT activity in S. cerevisiae is ATH1.

Ath1p, i.e. AT, has been reported to be necessary for S. cerevisiae to utilize extracellular trehalose as carbon source16. ATH1 deletion mutant of the yeast could not grow in the medium with trehalose as the carbon source.

Researchers have suggested that AT moves from its site of synthesis to the periplasmic space, where it binds exogenous trehalose to internalize it and hydrolyze it in the vacuoles . Recently it has been shown that more than 90% of AT activity in S. cerevisiae is extracellular and the hydrolysis of trehalose into glucose takes place at the periplasmic space. Previously, a highly glycosylated protein, gp37, which is the product of YGP1 gene, was reported to be co-purified with AT activity . Invertase activity was also reported to be co-purified with AT activity . The physical association of AT with these two proteins was thought to suffice for the AT to be secreted by invertase and gp37 secretion pathways in absence of any known secretion signal for Ath1p.

In a Candida utils strain, one regulatory a one non-regulatory trehalase were also reported . These two enzymes were reported to be distinguishable by their molecular weight, behavior in ion-exchange chromatography and kinetic properties. The regulatory trehalase appeared to be a cytoplasmic enzyme and the nonregulatory enzyme was mostly detected in vacuoles. But, in a more recent report, a C. utils strain was demonstrated to lack any detectable AT activity but contain only NT activity . AT activity was not detectable in this strain, though the strain was shown to utilize extracellular trehalose as carbon source.

Trehalose has been reported to be present as a storage carbohydrate in Pseudomonas, Bacillus, Rhizobium and in several actinomycetes and may be partially responsible for their resistance properties. Most of the trehalase enzymes isolated from bacteria have as optimum pH of 6.5-7.5. The trehalase enzyme of Mycobacterium smegmatis is a membrane bound protein . Periplasmic trehalase of Escherichia coli K12 is induced by growth at high osmolarity . The hydrolysis of trehalose into glucose takes place in the periplasm, and the glucose is then transported into the bacterial cell. Another cytoplasmic trehalase has also been reported from E. coli . The gene, which encodes this cytoplasmic trehalase, exhibits high homology to the periplasmic trehalase.

In S. cerevisiae at least two distinct trehalases have been reported. One was reported to be regulated by cAMP-dependent phosphorylation, . This enzyme activity was found in the cytosol. A second trehalase activity was found in the vacuoles of the same oraganism12. The pH optimum of cytosolic trehalse was found to be about 7.0 and thus, it was referred as neutral trehalase (NT); while the vacuolar trehalase enzyme was reported to be most active at pH around 4.5 and was termed as acid trehalase (AT). These two enzymes are encoded by two different genes – NTH1 and ATH1 respectively.

In plant kingdom, though trehalose has been reported from several pteridophytes including Selaginella lepidophylla and Botrychium lunaria; the sugar is rare in vascular plants and reported only in ripening fruits of several members of Apiaceae and in the leaves of the desiccation-tolerant angiosperm Myrothamnus flabellifolius . But, the enzyme trehalase is ubiquitous in plants . This is puzzling that trehalase is present in higher plants, though its substrate is absent. No clear role has been demonstrated for trehalase activity in plants. It has been suggested that trehalases could play a role in defense mechanisms or the enzyme could play a role in the degradation of trehalose derived from plant-associated microorganisms.

Trehalose has been reported to be present as a storage carbohydrate in Pseudomonas, Bacillus, Rhizobium and in several actinomycetes and may be partially responsible for their resistance properties. Most of the trehalase enzymes isolated from bacteria have as optimum pH of 6.5-7.5. The trehalase enzyme of Mycobacterium smegmatis is a membrane bound protein . Periplasmic trehalase of Escherichia coli K12 is induced by growth at high osmolarity . The hydrolysis of trehalose into glucose takes place in the periplasm, and the glucose is then transported into the bacterial cell. Another cytoplasmic trehalase has also been reported from E. coli . The gene, which encodes this cytoplasmic trehalase, exhibits high homology to the periplasmic trehalase.

One molecule of trehalose is hydrolyzed to two molecules of glucose by the enzyme trehalase. Enzymatic hydrolysis of trehalose was first observed in Aspergillus niger by Bourquelot in 1893. Fischer reported this reaction in S. cerevisiae in 1859. Since then the trehalose hydrolyzing enzyme, trehalase (?, ?-trehalose-1-C-glucohydrolase, EC 3.2.1.28) has been reported from many other organisms including plants and animals. Though trehalose is not known to be present in mammals, trehalase enzyme is found to be present in the kidney brush border membrane and the intestinal villae membranes . In the intestine the function of this enzyme is to hydrolyze ingested trehalose. Individuals with a defect in their intestinal trehalase have diarrhea when they eat foods with high trehalose content, such as mushrooms . Trehalose hydrolysis by trehalase enzyme is an important physiological process for various organisms, such as fungal spore germination, insect flight, and the resumption of growth in resting cells.

Trehalase is a glycoside hydrolase enzyme that catalyzes the conversion of trehalose to glucose. It is found in most animals.

The non-reducing disaccharide trehalose (?-D-glucopyranosyl-1,1-?-D-glucopyranoside) is one of the most important storage carbohydrates, which is present in almost all forms of life except mammals. The disaccharide is hydrolyzed into two molecules of glucose by the enzyme trehalase. There are two types of trehalases found in Saccharomyces cerevisiae, viz. neutral trehalase (NT) and acid trehalase (AT) classified according to their pH optima [4]. NT has an optimum pH of 7.0, while that of AT is 4.5.

Recently it has been reported that more than 90% of total AT activity in S. cerevisiae is extracellular and cleaves extracellular trehalose into glucose in the periplasmic space.

Sucrose itself is a non-reducing sugar, having the reducing aldehyde group involved in the glycosidic bond, and therefore will not test positive with Benedict’s solution. In order to test for sucrose, the enzyme sucrase is mixed with the sample. The sucrose is hydrolysed into glucose and fructose, with glucose being a reducing sugar, which will test positive with Benedict’s solution. Fructose can be isomerized to glucose by the addition of NaOH or other strong base.