Mutarotase

Related Reading

Mutarotase change the catalytic properties, substrate specificity or coenzyme specificity of these enzymes through controlled shearing, modification or mutation of natural enzyme genes, making them more in line with the needs of human social production and life an enzyme.

Introductions

At present, there are no fewer than thousands of enzymes that have been studied in the laboratory, but only a few of them are used. The main reason is that these enzymes are active under biological or natural conditions, but in actual production systems, their activity is extremely poor which cannot be applied. In industrial production, almost all reaction systems are in acid, alkali or solvent systems, and the temperature is relatively high, so most enzymes will be denatured under these conditions. Therefore, improving the stability of the enzyme is important in industrial production. Mutant enzymes cut, modify or mutate natural enzyme genes in a controlled manner, thereby changing the catalytic properties, substrate specificity or coenzyme specificity of these enzymes, making them more in line with the needs of human social production and life.

Figure 1. Protein structure of mutarotase.

Properties

• Improve enzyme activity

For example, after subtilisin Met222 is adapted to Cys, its catalytic activity is greatly improved.

• Improve enzyme stability

If Ile3 of T4 lysozyme is changed to Cys and then oxidized to form a disulfide bond with Cys97, the enzyme still has catalytic activity, but its stability is greatly improved.

• Change the substrate specificity

For example, after Gly216 or Gly226 in the trypsin substrate binding site is changed to Ala, the selectivity of the enzyme to the substrate is improved. Among them, the mutant enzyme Ala216 increased the Kcat/Km of the Arg-containing substrate, and Ala226 increased the Kcat/Km of the Lys-containing substrate.

• Change the optimal pH of the enzyme

After adapting the subtilisin Met222 to Lys, its optimum pH increased from 8.6 to 9.6.

• Change the requirement of enzyme for coenzyme

For example, the double mutant of dihydrofolate reductase (Arg44 is changed to Thr; Ser63 is changed to Glu) is more inclined to NADH2 than the original NADPH2.

• Change the allosteric regulatory function of the enzyme

For example, after the Tyr of Aspartate Transcarbamylase (ATC) is changed to Ser, the enzyme is deprived of allosteric regulation.

• Change other properties of the enzyme

Such as the modification of the redox ability of metalloenzymes and the modification of the structure of certain enzymes, so that some specific inhibitors can effectively act on the target site

Structural changes of mutant enzymes

1. Import disulfide bonds.

Proteins containing disulfide bonds are generally not easy to fold and have high stability, and this protein is not easy to denature even in organic solvents or abnormal physiological conditions. When disulfide bonds exist, the thermal stability of the enzyme is improved, and the more disulfide bonds, the more stable the enzyme.

2. The conformation of the peptide chain changes.

Local changes in the peptide chain conformation may lead to protein inactivation, thereby improving the thermal stability of the protein.

• Amino acid substitution

Amino acid substitution can often achieve the same purpose of improving protein thermal stability