Substrate Channeling

Synonyms

Enzymic mouth to mouth feeding

Definition

The preferred local utilization within a protein complex of a locally synthesized substrate by shielding the nascent substrate from a molar excess of the same moiety in the surrounding bulk solution. The converse also occurs where that moiety is preferentially drained by an intracomplex “substrate steal” mechanism depriving the complex of essential substrate. The direction of the flux also depends on the accessibility of the relevant precursor pools. Membrane-linked multienzymes in the glycolysis pathway attached to red cell transporter proteins and the fatty acid synthase multienzyme assembly are key examples. Reference Mies et al. (2007) and its recent update from the same group (J Biol Chem in press) provide a good example.

The relationship to cancer follows a newly discovered example that utilizes a protein–protein shield that includes one isoform of the first metastatic suppressor ever to be discovered, nucleoside diphosphate...