RESUMEN
Aldehyde dehydrogenase ST0064, the closest paralog of previously characterized allosteric non-phosphorylating glyceraldehyde-3-phosphate (GAP) dehydrogenase (GAPN, ST2477) from a thermoacidophilic archaeon, Sulfolobus tokodaii, was expressed heterologously and characterized in detail. ST0064 showed remarkable activity toward succinate semialdehyde (SSA) (Km of 0.0029 mM and kcat of 30.0 s(-1)) with no allosteric regulation. Activity toward GAP was lower (Km of 4.6 mM and kcat of 4.77 s(-1)), and previously predicted succinyl-CoA reductase activity was not detected, suggesting that the enzyme functions practically as succinate semialdehyde dehydrogenase (SSADH). Phylogenetic analysis indicated that archaeal SSADHs and GAPNs are closely related within the aldehyde dehydrogenase superfamily, suggesting that they are of the same origin.
Asunto(s)
Aldehído Deshidrogenasa/metabolismo , Gliceraldehído-3-Fosfato Deshidrogenasa (Fosforilante)/metabolismo , Succionato-Semialdehído Deshidrogenasa/genética , Sulfolobus/enzimología , Acilcoenzima A/genética , Acilcoenzima A/metabolismo , Aldehído Deshidrogenasa/genética , Secuencia de Aminoácidos , Gliceraldehído-3-Fosfato Deshidrogenasa (Fosforilante)/genética , Cinética , Filogenia , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , Succionato-Semialdehído Deshidrogenasa/metabolismoRESUMEN
Sulfolobus tokodaii, a thermoacidophilic archaeon, possesses two structurally and functionally different enzymes that catalyze the oxidation of glyceraldehyde-3-phosphate (GAP): non-phosphorylating GAP dehydrogenase (St-GAPN) and phosphorylating GAP dehydrogenase (St-GAPDH). In contrast to previously characterized GAPN from Sulfolobus solfataricus, which exhibits V-type allosterism, St-GAPN showed K-type allosterism in which the positive cooperativity was abolished with concomitant activation by glucose 1-phosphate (G1P). St-GAPDH catalyzed the reversible oxidation of GAP to 1,3-bisphosphoglycerate (1,3-BPG) with high gluconeogenic activity, which was specific for NADPH, while both NAD(+) and NADP(+) were utilized in the glycolytic direction.