What is the benefit of substrate channeling? The PDH active site forms in the hydrophobic core of the complex instead of a surface‑exposed region. Reaction intermediates move to sequential active sites faster than the diffusion constant. Every intermediate or product made by the PDH complex enters the citric acid cycle as a substrate. The PDH complex sequesters excess substrate to use at later time. Intermediates of a multistep reaction sequence do not dissociate from the enzyme complex.

Substrate channeling is the process in which intermediates produced in an enzymatic reaction is transferred to another enzyme or active in a reaction pathway without the substrate having to dissociate from the enzymes active sites into the reaction medium or solution.

Benefits of substrate channeling include:

intermediates of a multistep reaction sequence do not diffuse away from the catalytic sites of enzymes in the pathway thereby ensuring that their concentration remains high

there is greater control of the flow metabolites in the pathway
other competing enzymes for a common substrate do not make use of the substrates
increased efficiency of the catalytic process

Substrate channeling is observed in the pyruvate dehydrogenase complex reaction which oxidizes pyruvate to acetyl-CoA.