An enzymatic reaction occurs as follows: S þ NADþ ¼ P þ NADH. In order to assess the enzyme, the progress of the reaction was determined by recording NADH absorbance at 340 nm (molar absorptivity: a ¼...

An enzymatic reaction occurs as follows: S þ NADþ ¼ P þ NADH. In order to assess the enzyme, the progress of the reaction was determined by recording NADH absorbance at 340 nm (molar absorptivity: a ¼ 6200 L mole1 cm1 ) in a l ¼ 1 cm cell containing V ¼ 3 ml solution. The absorbance (A) varied linearly with time at the beginning and changed by DA ¼ 0:26 units within the time interval Dt ¼ 590 s. a. What is the role of NADþ in this reaction? b. Calculate the enzyme activity in katal and enzyme units. c. Calculate the specific enzyme activity assuming that the solution contains 0.02 mg enzyme. Hints and answers: Convert all quantities into SI units. Ds is proportional to DA, in accordance to Beer’s law. Activity ¼ 0.84 nanokatal ¼ 0.05 U. Specific activity ¼ 42 mkatal/s kg ¼ 2.5 U/m