637 Quiz 3

________ is the maximum initial velocity an enzyme can have.

Vmax

Which one of the four rate constants (k?) is assigned to the step in an enzyme-catalyzed reaction that involves the binding of enzyme to substrate (formation of an ES complex)?

k1

Which one of the four rate constants (k?) is also known as the turnover number?

kcat

What class of enzymes does DNA polymerase belong to?

Transferases

What class of enzymes does wheat germ acid phosphatase belong to?

Hydrolases

When [S] = KM, what is the relationship between v0 and Vmax?

v0 = 1/2 Vmax

In a Lineweaver-Burk plot of competitive inhibition which axis do the plotted lines converge on? Does this mean they share the same Vmax or the same KM?

They converge at the Y-intercept. Share the same Vmax (y-int = 1/Vmax).

Define specific activity.

Activity of an enzyme per milligram of total protein (expressed in μmol/(min*mg)). Micromoles of product formed by an enzyme in a given amount of time.

An enzyme with a single active site per molecule at a concentration of 0.010 millimolar has a Vmax of 10.0 millimolar per minute. What is its turnover number (be sure to include units.) What would your answer be if there were two active sites per molecule for that enzyme?

Kcat is turnover number. Kcat = Vmax/[Et] = (10.0mMproduct/min)/(0.010mMenzyme) = 1000 mMproduct/mMenzyme*min. If there were two active sites, Kcat = (10.0mMproduct/min)/(0.010mMenzyme*2) = 500 mMproduct/mMenzyme*min.