How Do You Calculate Km in Multi-Step Enzyme Kinetics?

[PPapadopoulos]

The problem asks to consider the following reaction:
S + E =ES1=ES2---> P + E where = between S + E and ES1 has a forward reaction constant of k1 and a reverse constant of K2. The = between ES1 and ES2 has a forward reaction of k3 and a reverse of k4 and ----> has a k5 forward reaction constant. I need to solve for ES2 to plug into the equation v=k5[ES2]. I am having a lot of trouble finding Km which is the Michaelis-Menton Constant. Any help would be greatly appreciated.

 

[epenguin]

Need to complete the question which already would point you to getting the answer.

From context I deduce you want to know the steady-state [ES2]. What is the steady state? It's when, after an initial build-up from [ES1] = 0, [EP1] = 0 these and [E] settle down to a constant concentration in a constant throughput.

What does 'constant concentration of EP2 ' say about d[EP2]/dt? And how is that related in simple physical chemical laws to the concentrations of the various species in your mechanism?
Similarly for d/dt of the other enzymic species.

Just jogging memory as I'm sure some example would have been done in your lecture or book.

After setting up equations you also have to solve them, but it's the setting up that seems to cause most students' problems.