Cellobiase

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Introductions

Cellobiase, also known as β-glucosidase, can hydrolyze cellobiose to produce two molecules of glucose, and greatly promote the hydrolysis of endoglucanase and exoglucanase to accelerate the overall hydrolysis of cellulose enzyme system and promote more complete hydrolysis of cellulose. Cellobiase belongs to the class of cellulases and is an important component of the cellulolytic enzyme family, capable of hydrolyzing the β-D-glucose bond bound to the terminal non-reducing bond, while releasing β-D-glucose and the corresponding ligand.

Figure 1. Structure of cellobiase.

Structure

Cellobiase consists of two polypeptide chains. Each chain consists of 438 amino acids that form a subunit of the enzyme. Each of these subunits contains an active site. The active site has three potential components: pockets, clefts and tunnels. The pocket structure facilitates the recognition of monosaccharides like glucose. The cleft allows for the binding of sugars to form polysaccharides. The tunnels allow the enzyme to attach to the polysaccharide and then release the product while still attached to the sugar.

Screening for β-glucosidase inhibitors

Cellobiase are involved in the pathogenesis of various diseases such as diabetes, AIDS, metastatic cancer and lysosomal storage disease. Therefore, screening for efficient β-glucosidase inhibitors can not only reveal the key functions of enzymes in the life system by blocking specific metabolic processes, but also provide promising therapeutic approaches for the treatment of related diseases. Cellobiase inhibitors are screened by the degree of inhibition of β-glucosidase catalytic substrate hydrolysis reactions by inhibitory factors.

Function

The function of cellobiase is to carry out hydrolysis of various glycosides and oligosaccharides. The most important oligosaccharide β-glucosidases react with cellulose. Cellobiase is necessary for many organisms to consume this enzyme to complete the double substitution reaction, which means that the enzyme becomes the intermediate form when the first substrate enters the active site, then releases the product before the other substrate binds, and at the end of the reaction reverts to its original form. In the case of β-glucosidase, the active site involves two carboxylic acid residues of glucoside, cellobiose, cello-triose, and cello-tetrasaccharide. The purpose of the reaction is to remove residues from the disaccharide cellobiose during the hydrolysis of the biomass to produce glucose. Depending on the reaction of the enzyme with the end product, it will be one or two glucose molecules.

Cellobiase assay

• Spectrophotometric method

Most inorganic compounds, organic compounds and proteins have characteristic light absorption in the violet or visible region, or can be converted into certain derivatives with specific absorption.

• Fluorescence method

The fluorescence method refers to the transformation of certain molecules from the ground state to the excited state after the absorption of energy by external radiation, and the luminescence of the excited molecule when it jumps back to the ground state.

• Electrochemical methods

Because cellobiase catalyzed hydrolysis of substrates generally produces glucose molecules. The electrochemical method has the advantages of better accuracy, precision, reproducibility, stability, durability and selectivity.

• Reagent kit method

Glucose production from cellobiase catalyzed substrate hydrolysis can be quantified by a commercial glucose kit, which characterizes the activity of cellobiase in the sample to be tested based on the glucose content.

Conclusions

Cellobiases have important applications in the food industry, biofuels and medical testing. We have described the common methods for measuring cellobiase activity and its structure and function. Since cellobiases play an important role in both primary and secondary metabolic activities of organisms, it is crucial to further analyze the effects of cellobiases on life activities and various physiological functions.