[3] Channeling can make a metabolic pathway more rapid and efficient than it would be if the enzymes were randomly distributed in the cytosol, or prevent the release of unstable intermediates.
One possibility, which occurs in the pyruvate dehydrogenase complex, is by a substrate being attached to a flexible arm that moves between several active sites (not very likely).
Some authors have maintained that direct transfer of NADH from one enzyme as product to another as substrate is a common phenomenon.
[8] However others, such as Gutfreund and Chock[9] and Pettersson[10] have argued that the experimental evidence is too weak to support such a conclusion.
In a more recent study[11] Svedružić and colleagues conclude that such direct transfer is a real phenomenon, but they sound a note of caution:Our results also show that it is impossible to design experiments that can conclusively analyze substrate channeling in cells if we do not understand the underlying molecular principles and the properties of the related enzymes.It is sometimes suggested, for example by Ovádi,[12] that metabolite channeling decreases the concentration of metabolite in free solution.