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  • Title: The crystal structure of a class II fructose-1,6-bisphosphate aldolase shows a novel binuclear metal-binding active site embedded in a familiar fold.
    Author: Cooper SJ, Leonard GA, McSweeney SM, Thompson AW, Naismith JH, Qamar S, Plater A, Berry A, Hunter WN.
    Journal: Structure; 1996 Nov 15; 4(11):1303-15. PubMed ID: 8939754.
    Abstract:
    BACKGROUND: [corrected] Aldolases catalyze a variety of condensation and cleavage reactions, with exquisite control on the stereochemistry. These enzymes, therefore, are attractive catalysts for synthetic chemistry. There are two classes of aldolase: class I aldolases utilize Schiff base formation with an active-site lysine whilst class II enzymes require a divalent metal ion, in particular zinc. Fructose-1,6-bisphosphate aldolase (FBP-aldolase) is used in gluconeogenesis and glycolysis; the enzyme controls the condensation of dihydroxyacetone phosphate with glyceraldehyde-3-phosphate to yield fructose-1,6-bisphosphate. Structures are available for class I FBP-aldolases but there is a paucity of detail on the class II enzymes. Characterization is sought to enable a dissection of structure/activity relationships which may assist the construction of designed aldolases for use as biocatalysts in synthetic chemistry. RESULTS: The structure of the dimeric class II FBP-aldolase from Escherichia coli has been determined using data to 2.5 A resolution. The asymmetric unit is one subunit which presents a familiar fold, the (alpha/beta)8 barrel. The active centre, at the C-terminal end of the barrel, contains a novel bimetallic-binding site with two metal ions 6.2 A apart. One ion, the identity of which is not certain, is buried and may play a structural or activating role. The other metal ion is zinc and is positioned at the surface of the barrel to participate in catalysis. CONCLUSIONS: Comparison of the structure with a class II fuculose aldolase suggests that these enzymes may share a common mechanism. Nevertheless, the class II enzymes should be subdivided into two categories on consideration of subunit size and fold, quaternary structure and metal-ion binding sites.
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