Question

This problem is similar to the previous problem, but the parameter values are slightly different. Once again, an experimenter is working with an enzyme that, on a per milligram basis, produces a certain number of \mu μ mol of product per minute at optimal temperature and pH. The product of the enzyme-catalyzed reaction is a desirable fine chemical, and thus the researcher designs a pilot biosynthetic reaction to produce a target number of \mu μ mol of the desired product. The experimenter starts the reaction by adding 1.0 milligram of the enzyme. The rate of product formation reveals that the enzyme activity is normal. (The researcher is able to continually remove the product as it is produced.) To the astonishment of the experimenter, an assistant inexplicably adds some sodium hydroxide to the reaction after 1 min. (The assistant misunderstood the protocol.) Thirty seconds after the reaction was stopped by the addition of the NaOH, the experimenter adds additional buffer and is pleased to see that the reaction is proceeding again, but at 76% of its normal activity. Furthermore, it takes 3½ minutes longer to produce the target amount of product than it should have. Had the enzyme been allowed to produce an additional 90 \mu μ mol of product prior to the addition of base, and then, 30 seconds later, the addition of buffer, it would have taken 3 minutes longer to produce the target number of \mu μ mol of product. Given this information, what was the target amount of product (in \mu μ mol) that was desired? To answer this question, you will have to first of all determine the specific activity of the enzyme (\mu μ mol of product per minute per milligram of enzyme), which is what you did to solve the previous problem. Enter your answer to the nearest ones.

Answer 1

Specific activity of an enzyme is the number of moles of product formed by an enzyme in a given amount of time (minutes) under given conditions per milligram of total proteins. The unit is μmol mg⁻¹ min⁻¹.

Time taken for production of 90 micromol of product before addition of NaOH for 1 mg of protein: 3 minutes

Therefore

Specific activity of the enzyme: 30 μmol min⁻¹mg⁻¹

Total time taken for production of the product: 4 minutes

Target amount of product (in µmol) in 4 minutes: 120 μmol