Ferredoxin-ferredoxin NADP reductase interaction:catalytic differnces between the soluble and thylakoid-bound complex

Ferredoxin-NADP reductase (FNR) and ferredoxin form a complex when the former is membrane-bound
as they do when both components are in solution, with the same dissociation constant. The rate constant
of NADP photoreduction, first order with respect to the complex, is more than 20-times higher when FNR
is membrane-bound than when the enzyme is in solution. The Arrhenius activation energy is identical in
both conditions. These observations are interpreted in terms of ‘entropic catalysis’ of NADP reduction
by the thylakoid-bound FNR.