[Organization of enzymes on subcellular structures: relay at the surface].
There is a large body of evidence that soluble cytoplasmic enzymes of eukaryotic cells, e.g., glycolytic enzymes and proteins of the translational machinery, are organized in some way in space and in time. The following features of such organization emerge from the experimental data: (1) metabolites are transferred between enzymes directly "from hand to hand" in short-living enzyme-enzyme complexes rather than by diffusion in aqueous media; (2) enzymes show a tendency to be absorbed on surfaces of subcellular structures, such as membranes, cytoskeleton and polyribosomes; (3) enzymes are desorbed from a surface of a subcellular structure after binding specific metabolites, i.e., substrates and/or products of the reactions catalyzed by these enzymes. These features are suggestive of a relay mechanism for the enzyme systems functioning in a cell; an enzyme adsorbed on a surface of a subcellular structure is desorbed after binding its substrate or in the course of the catalytic act. Within a complex with its product the enzyme diffuses into the environment, until it reaches the next enzyme adsorbed on the same surface; then a short-living enzyme-enzyme complex is formed, and a direct "from hand to hand" transfer of the metabolite takes place. As a result, the overall metabolic process appears to be localized near the surface. We termed this mechanism as a "relay at the surface".
Riazanov
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Spirin
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D003593:Cytoplasm / Q000201:enzymology; D003599:Cytoskeleton / Q000201:enzymology; D004798:Enzymes / Q000378:metabolism*; D005057:Eukaryotic Cells / Q000201:enzymology; D007425:Intracellular Membranes / Q000201:enzymology*; D046911:Macromolecular Substances; D008954:Models, Biological; D011132:Polyribosomes / Q000201:enzymology
D004798:Enzymes; D046911:Macromolecular Substances
Organizatsiia fermentov na vnutrikletochnykh strukturakh: éstafeta u poverkhnosti.