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BACKGROUND: Oligomers and separate subunits of the glycolytic enzymes oftenhave different catalytic properties. However, spectral data show an apparent lack of significant conformationalchanges during oligomerization. Since the conformation of an enzyme determines its catalytic properties,the structural mechanism(s) influencing the activity is of considerable interest. MATERIAL/METHODS: Analysisof the spatial structures of the junctions between interglobular contacts and binding sites may givea clue to the mechanism(s) of the activation. In this work, the problem was studied using available structuraland biochemical data for the oligomeric enzymes of glycolysis. RESULTS: Computational analysis of thestructures of the junctions has identified three structurally distinct types of junctions: 1. interglobularbinding site (2 of 8 enzymes); 2. domain-domain stabilization (5 of 8); and 3. 'sequence overlap' ora local conformational change (all enzymes). Thus the catalytic activity may be influenced through theshifts of the modules of protein structure (types 1, 2) and/or due to a slight change in the local structure(type 3). The more common junctions of types 2 and 3 are well conserved among eukaryotic enzymes, whichsuggests their biological importance. CONCLUSIONS: The results suggest that a profound and a complexchange in conformation in subunits of an oligomeric enzyme may not be necessary for a significant changein the catalytic properties. The analysis maps the residues important for the junctions and thus forthe link between the catalytic activity and the oligomeric state of the enzymes.