enzymes question, biochemistry?

[faciology]

1.
An enzyme can accept a variety of substrates. Substrate #1 has a Km of 5 mM and a kcat of 100 sec-1. Another substrate, substrate #2, has a Km of 10 mM and a kcat of 150 sec-1. Which substrate is the better substrate? Why?




2.
If the specific activity for an enzyme is 100 ?moles product mg-1 sec-1 (assay volume = 1 mL), what is the Kcat? The MW of the enzyme is 60,000.




3.
An enzyme (that shows Michaelis Menten kinetics) has a Km of 2 mM, and different enzyme (also with MM kinetics) that catalyzes the same reaction has a Km value of 6 mM. Comment on the dependence of the rate of the reaction (for each enzyme) on the concentration of substrate in the 4-7 mM range.