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Publication Abstract from PubMed

Invertase is an enzyme widely distributed among plants and microorganisms that catalyzes the hydrolysis of the disaccharide sucrose into glucose and fructose. Despite the important physiological role of Saccharomyces invertase and the historical relevance of this enzyme as a model in early biochemical studies, its structure had not yet been solved. We report here the crystal structure of recombinant Saccharomyces invertase at 3.3 A resolution showing that the enzyme folds into the catalytic beta-propeller and beta-sandwich domains characteristic of GH32 enzymes. However, Saccharomyces invertase displays an unusual quaternary structure. Monomers associate in two different kinds of dimers that are in turn assembled into an octamer, best described as a tetramer of dimers. Dimerization plays a determinant role in substrate specificity because this assembly sets steric constrains that limit the access to the active site of the disaccharide (sucrose) or short oligosaccharides of up to four units. Comparative analysis of GH32 enzymes shows that formation of the Saccharomyces invertase octamer occurs through a beta-sheet extension that seems unique to this enzyme. Interaction between dimers is determined by a short amino acid sequence at the beginning of the beta-sandwich domain. Our results highlight the role of the non-catalytic domain in fine-tuning substrate specificity and thus supplement our knowledge on the activity of this important family of enzymes. This, in turn, gives a deeper insight into the structural features that rule modularity and protein-carbohydrate recognition.

The three-dimensional structure of Saccharomyces invertase: role of a non-catalytic domain in oligomerization and substrate specificity.,Sainz-Polo MA, Ramirez-Escudero M, Lafraya A, Gonzalez B, Marin-Navarro J, Polaina J, Sanz-Aparicio J J Biol Chem. 2013 Feb 21. PMID:23430743^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.