Phosphatases are involved in regulating enzyme activity of other enzymes. Briefl
ID: 1065926 • Letter: P
Question
Phosphatases are involved in regulating enzyme activity of other enzymes. Briefly describe one specific example of an enzyme whose activity is regulated by a phosphatase. Give a reasonable explanation of why high concentrations of ammonium sulfate cause proteins to precipitate from an aqueous protein solution. The substrate that was used to investigate the enzymatic activity of wheat bran phosphatase was p-nitrophenylphosphate. It is converted to p-nitrophenol and phosphate by this enzyme. P- Nitrophenol has a pKa of 7.1 and is colorless, while its conjugate base, p-nitrophenoxide has a yellow color. The enzyme assay was performed at pH 5.1. After the 0.5M KOH was added at the end of each kinetic run, the pH of the assay mixture was 9.1. Why was the base added?Explanation / Answer
1. Phosphorylation is the addition of a phosphate group (PO4)3 to a molecule. The phosphate group can attract positively charged groups and repel negatively charged groups. These changes the conformation of an enzyme to a more active or inactive way by phosphorylation.
An example is the glycogen phosphorylation that breaks down glycogen inti glucose.
2. Addition of ammonium sulfate to an aqueous protein solution alters the solubility of the solution. The solubility varies with ionic strength. At low ammonium sulfate concentration, ionic strength increases with ammonium sulfate concentration and solubility of proteins increases. This is known as salting in. However, with increasing concentration of ammonium sulfate (high ionic strength), the solubility of the protein begins to decrease and at very high concentration of ammonium sulfate, the protein will be precipitated from the solution. This is known as salting out.