Bob Phair asked: "I have, however, always wondered what sorts of errors
I might be introducing if the underlying mechanism was not truly rapid
equilibrium. I wonder if Athel or anyone else could offer some
advice..."
This is one of those things that was much more thoroughly discussed in
the past than it tends to be nowadays, and the references I know of are
quite old. Mo Cleland studied the question in the context of
galactokinase [J. S. Gulbinsky & W. W. Cleland (1968) Biochemistry 7,
566-575] and came to the conclusion that the deviations in observable
behaviour that the algebra suggests one should see will usually be too
small to detect. I think this is probably true as a general conclusion,
though improvements in measurement techniques may mean one can detect
things in 1997 that one couldn't have detected in 1968. To put it simply
(possibly too simply) you can usually assume that the rate equations
derived from oversimplified models will describe the behaviour quite
accurately, BUT you CANNOT assume that the numerical values of the
kinetic parameters have any meaning.
