Final answer:
Limit dextrin is the remainder of a glycogen molecule after phosphorylase has cleaved glucose units until only four remain before a branching point. These structures accumulate in liver and kidney tissues under certain hormonal conditions. Dextrin substances, including limit dextrin, have various uses in industrial and food applications.
Step-by-step explanation:
Limit dextrin refers to a particular type of dextrin that results from the action of the enzyme phosphorylase on glycogen. When glycogen is degraded by phosphorylase, the enzyme cleaves glucose units from the non-reducing ends of the glycogen molecule until it reaches a point four units away from a branching point. At this juncture, phosphorylase cannot continue, and the remnants are known as limit dextrins, which still contain the branched structure of glycogen but are of significantly reduced size. Limit dextrins can accumulate in tissues such as the liver and kidney, particularly when blood sugar levels are low and are not increased by hormones like epinephrine or glucagon. Lysosomes can contain enzymes necessary to further degrade these limit dextrins.
Dextrins are intermediate-sized glucose polysaccharides that have various industrial and food-related uses due to their unique properties, such as stickiness when wet and easy digestibility. An example is their use in the commercial preparation of infant foods. Another type of dextrin is dextran, which is not to be confused with limit dextrin. Dextran, produced by yeasts and bacteria, consists of α-D-glucose linked by α-1→6 glycosidic linkages and is used in medical applications, such as a plasma substitute.