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  • Title: An extremely thermostable aldolase from Sulfolobus solfataricus with specificity for non-phosphorylated substrates.
    Author: Buchanan CL, Connaris H, Danson MJ, Reeve CD, Hough DW.
    Journal: Biochem J; 1999 Nov 01; 343 Pt 3(Pt 3):563-70. PubMed ID: 10527934.
    Abstract:
    Sulfolobus solfataricus is a hyperthermophilic archaeon growing optimally at 80-85 degrees C. It metabolizes glucose via a novel non-phosphorylated Entner-Doudoroff pathway, in which the reversible C(6) to C(3) aldol cleavage is catalysed by 2-keto-3-deoxygluconate aldolase (KDG-aldolase), generating pyruvate and glyceraldehyde. Given the ability of such a hyperstable enzyme to catalyse carbon-carbon-bond synthesis with non-phosphorylated metabolites, we report here the cloning and sequencing of the S. solfataricus gene encoding KDG-aldolase, and its expression in Escherichia coli to give fully active enzyme. The recombinant enzyme was purified in a simple two-step procedure, and shown to possess kinetic properties indistinguishable from the enzyme purified from S. solfataricus cells. The KDG-aldolase is a thermostable tetrameric protein with a half-life at 100 degrees C of 2.5 h, and is equally active with both d- and l-glyceraldehyde. It exhibits sequence similarity to the N-acetylneuraminate lyase superfamily of Schiff-base-dependent aldolases, dehydratases and decarboxylases, and evidence is presented for a similar catalytic mechanism for the archaeal enzyme by substrate-dependent inactivation by reduction with NaBH(4).
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