Question

The hydrolysis of pyrophosphate to orthophosphate is important in driving forward biosynthetic reactions such as the synthesis of DNA. This hydrolytic reaction is catalyzed in Escheria coli by a pyrophosphatase that has a mass of 120 kd and consists of six identical subunits. For this enzyme, a unit of activity is defined as the amount of enzyme that hydrolyzes 10micromol of pyrophosphate in 15 minutes at 37 degrees Celsius under standard assay conditions. The purified enzyme has a V_maxof 2800 units per milligram of enzyme. How many moles of substrate is hydrolyzed per second per milligram of enzyme when the substrate concentration is much greater than K_m? How many moles of of active sites is there in 1 mg of enzyme? Assume that each subunit has one active site. What is the turnover number of the enzyme?

Answer 1