Enzyme kinetics

[bascombn at pt.cyanamid.com]

I haven't seen a specific question related to enzyme kinetics here previously
but I am hoping someone can help me out. I am trying to find/remember
on kinetic characteristics of multisubunit enzymes that form one active site 
from two subunits. Two subunit for two active sites but the "pocket" is actually
at the interface of the two subunits. If I recall it was sonething like
"half-of-the-sites reactivity" but cannot dig up a reference yet.

Any recommendations?

Thanks in advance