Β-Glucosidase

Class of enzymes

β Glucosidase (; systematic name β D glucoside glucohydrolase) is an enzyme that catalyses the following reaction:
Hydrolysis of terminal, non reducing β D glucosyl residues with release of β D glucose

β Glucosidase is composed of two polypeptide chains. Each chain is made up of 438 amino acids and constitute a subunit of the enzyme. Each of these subunits contains an active site. The active site has three potential components: the pocket, the cleft, and the tunnel. The pocket structure is beneficial for recognition of monosaccharide like glucose. The cleft allows for binding of sugars to form polysaccharides. The tunnel allows for the enzyme to attach to polysaccharide and then release product while still attached to the sugar. In the case of β glucosidase, two carboxylate residues of glucosides, cellobiose, cellotriose, cellotetraose are involved at the active site. The purpose of the reaction is to remove the residues from disaccharide cellobiose to produce glucose during the hydrolysis of biomass. Depending on what the enzyme is reacting with the end product will be one or two glucose molecules.

Humans are unable to digest cellulose of plants cells. This is because the enzyme is not present in the human stomach, as the optimal pH is 5.6, while the pH of a human's stomach is acidic (between 1.5 and 3.5). However, humans do require β glucosidase, Lysosomal β glucosidase, as it plays an important role in the degradation of glycosphingolipids. The enzyme will break down glucosylceramide into ceramide and glucose. If an accumulation occurs this will lead to Gaucher disease. The buildup of fatty substances can lead to weakening bones, liver damage, and enlarging and impairing the function the spleen.

Bonnethead sharks are found in tropical and subtropical water living in estuaries with muddy or sandy bottoms, rich with seagrass. They were once thought of as being solely carnivores. It was known that bonnethead did consume seagrass, but it was viewed as incidental and dismissed as not helping the benefitting the shark. However, recent studies of the shark's hindgut has found that it has a high activity level of β glucosidase. During the digestive process of the bonnethead shark, the acidic stomach weakens the cell walls of the seagrass and allows for β glucosidase to enter the cell and digest the cellulose. The activity level is on par with the monkeyface eel. The monkeyface eel is a herbivore, meaning that the bonnethead is able to perform the same digestive activity as a herbivore. Therefore, the bonnethead shark is now classified as an omnivore.