Toward an evaluation of metabolite channeling in vivo

Intermediates of metabolic pathways are sometimes contained within cavities of enzyme molecules and passed directly from active centers of one to next enzymes without diffusing into bulk matrix. This 'metabolite channeling' is postulated to have various advantages in enhancing and regulating pathway reactions and considered as a central unit to control metabolic network. Therefore, it has a strong potential in applications to metabolic engineering to enhance the production of desired molecules. Quantitative evaluation of the effects of metabolite channeling is crucial for its appropriate application and further understanding of its functions. In the present review, current approaches to demonstrate functional metabolite channeling will be reviewed and their extension toward quantitative evaluation of channeling effects in vivo will be discussed.