Mixed-linkage glucan (MLG), sometimes incorrectly referred to as

beta-glucan Beta-glucans, β-glucans comprise a group of β-D-glucose polysaccharides (glucans) naturally occurring in the cell walls of cereals, bacteria, and fungi, with significantly differing physicochemical properties dependent on source. Typically, � ...

, is a hemicellulosic

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with w ...

consisting of β-D(1-3) and β-D(1-4) linked glucosyl residues. MLG is highly prevalent within the

Poales The Poales are a large order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges. Sixteen plant families are currently recognized by botanists to be part of Poales. Descriptio ...

, where it has important properties in the

diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...

. In addition, although thought to be confined to the Poales, MLG has been found to be highly prevalent in

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...

of the distantly related

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Equisetum ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass ...

''.

Structure

MLG is composed of β-D(1-3) and β-D(1-4)-linked glucosyl residues. Typically there are regions of 2-5 β-D(1-4)-linked residues separated by β-D(1-3)-linkages. The β-D(1-4)-linked residues form rigid regions of the structure while the β-D(1-3)-links are flexible.

Roles in the diet

MLGs exhibit the

physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemica ...

properties of

dietary fibre Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by the ...

s and the functional properties of

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...

and gel-forming food

hydrocolloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

s.{{cite journal , doi=10.1016/j.jcs.2007.05.003 , last1=Lazaridou , first1=A. , last2=Biliaderis , first2=C.G. , year=2007 , title=Molecular aspects of cereal β-glucan functionality: Physical properties, technological applications and physiological effects , journal=Journal of Cereal Science , volume=46 , issue=2 , pages=101–118

Functions in plants

The prevalence of MLG within the poales and ''Equisetum'' suggests a definite role in their growth. However the presence of the

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

mixed-linkage glucan : xyloglucan endotransglucosylase within ''Equiseta'' suggest that the role of MLG in each may be different.

References

Polysaccharides

Structure

Roles in the diet

Functions in plants

See also

References