NADP-dependent dehydrogenase with broad substrate specificity acting on 3-hydroxy acids. Catalyzes the NADP-dependent oxidation of L-allo-threonine to L-2-amino-3-keto-butyrate, which is spontaneously decarboxylated into aminoacetone. Also acts on D-threonine, L-serine, D-serine, D-3-hydroxyisobutyrate, L-3-hydroxyisobutyrate, D-glycerate and L-glycerate. L-allo-threonine + NADP(+) = aminoacetone + CO2 + NADPH L-allo-threonine + NADP(+) = (2S)-2-amino-3-oxobutanoate + H(+) + NADPH The highest catalytic efficiency was observed with L-allo-threonine. Optimum pH is about 8.5 for the oxidation of L-serine. Stable from pH 7.5 to 10.5. Stable up to 40 degrees Celsius. Homotetramer. Present with 3210 molecules/cell in log phase SD medium. Belongs to the short-chain dehydrogenases/reductases (SDR) family.