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 E. coli by a pyrophosphate 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 10 umol of pyrophosphate in 15 min at 37 degrees C under standard assay conditions. The purified enzyme has a Vmax of 2800 units per milligram of enzyme.

a) How many moles of the substrate is hydrolyzed per second per milligram of enzyme when the substrate concentration is much greater than Km? (Draw a velocity versus substrate concentration graph to show your point)

b) How many moles of active sites is there in 1 mg of enzyme? Assume that each subunit has one active site.
c) What is the turnover number of the enzyme? (Don’t bother comparing it to other enzymes; just show all your own, which equations you use, what numbers you use, where you get them from, etc.)