Implications of Metabolic Compartmentation in Prokaryotic Cells

Abstract

Contemplation of the sheer complexity of cellular metabolism, coupled with the realization that in bacterial cells it all takes place in a minute volume exhibiting a minimum of cellular architectural detail, soon begins to prompt questions about the nature of intracellular organization in prokaryotic cells. The very absence of membrane-bounded organelles suggests that, aside from reactions localized in or about the cell membrane, organizational structure is likely to be based on direct macromolecular interactions. These would yield macro structures which in some cases might also act in a more-or-less compartmentalized fashion, leading to the separate channelling of whole series of sequential reactions. There is some variation in the way in which the terms “compartment” and “channel” are used. In the present contribution a “channel” is defined as a structure or a facet of organization which acts as a constraint to free chemical diffusion. A “compartment” is a sequestered volume; it may be similar to a channel. Any defined aspect of biochemical organization may represent a compartment so long as it remains chemically inactive. For example, a ligand bound to an enzyme is in a compartment until it undergoes a reaction.