The enzyme carboxypeptidase catalyses the hydrolysis of polypeptides, and here we consider its inhibition. the following results were obtained when the rate of the enzymolysis of carbobenzoxy-glycyl-d-phenylalanine (cbgp) was monitored without inhibitor:

[cbgp] (m) 1.25×10-2 3.84×10-2 5.81×10-2 7.13×10-2

uninhibited relative reaction rate 0.398 0.669 0.859 1.00

(all rates in this exercise were measured with the same concentration of enzyme and are relative to the rate measured when [cbgp] = 0.0713 m in the absence of inhibitor.) when 2.0 mm phenylbutyrate ion was added to a solution containing the enzyme and substrate, the following results were obtained:

[cbgp] (m) 1.25×10-2 2.50×10-2 4.00×10-2 5.50×10-2

inhibited relative reaction rate 0.172 0.301 0.344 0.548

in a separate experiment, the effect of 50 mm benzoate ion was monitored and the results were:

[cbgp] (m) 1.75×10-2 2.50×10-2 5.00×10-2 10.00×10-2

inhibited relative reaction rate 0.183 0.201 0.231 0.246

(a) use lineweaver-burk plots and determine vmax and km for the uninhibited and inhibited reactions. are the inhibitors competitive or noncompetitive? * do not forget to hand in both graphs and worksheets! you may plot all three experiments on one graph.

(b) find ki for both inhibitors.