Functional maps of the junctions between interglobular contacts and active sites in glycolytic enzymes -- a comparative analysis of the biochemical and structural data

Oligomers and separate subunits of the glycolytic enzymes often have different catalytic properties. However, spectral data show an apparent lack of significant conformational changes during oligomerization. Since the conformation of an enzyme determines its catalytic properties, the structural mechanism(s) influencing the activity is of considerable interest.Analysis of the spatial structures of the junctions between interglobular contacts and binding sites may give a clue to the mechanism(s) of the activation. In this work, the problem was studied using available structural and biochemical data for the oligomeric enzymes of glycolysis.Computational analysis of the structures of the junctions has identified three structurally distinct types of junctions: 1. interglobular binding site (2 of 8 enzymes); 2. domain-domain stabilization (5 of 8); and 3. 'sequence overlap' or a local conformational change (all enzymes). Thus the catalytic activity may be influenced through the shifts 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, which suggests their biological importance.The results suggest that a profound and a complex change in conformation in subunits of an oligomeric enzyme may not be necessary for a significant change in the catalytic properties. The analysis maps the residues important for the junctions and thus for the link between the catalytic activity and the oligomeric state of the enzymes.