Trivalent metal ions promote the malic enzyme-catalyzed building of carbon–carbon bonds from CO2 and pyruvate

Abstract

Malic enzyme (ME) from chicken liver (EC 1.1.1.40) is an enzyme that catalyzes the decarboxylation of malate into pyruvate and CO₂ and the reverse reaction that introduces CO₂ as a carboxy-group to pyruvate to form malate via oxaloacetate in the presence of natural co-enzyme NADP⁺/NADPH. Thus, ME is an attractive biocatalyst for building carbon–carbon bonds through the carboxylation of pyruvate with CO₂. Since ME mainly catalyzes the decarboxylation of malate to produce pyruvate via oxaloacetate, it is necessary to devise ways to promote the carboxylation of pyruvate with CO₂ to produce oxaloacetate based on the building of carbon–carbon bonds. Enhancing the carboxylation of pyruvate by the addition of metal ions with CO₂ and using ME as a catalyst will lead to new insight into biocatalytic CO₂ utilization research. The effect of adding divalent and trivalent metal ions to promote the ME-catalyzed building of carbon–carbon bonds through the carboxylation of pyruvate with CO₂ was investigated. Specifically, it was found for the first time that the addition of trivalent aluminium and iron ions accelerates ME-catalyzed carboxylation of pyruvate with CO₂. Moreover, it was found that a high concentration of aluminum ions (>100 μM) and a low concentration of iron ions (<10 μM) promote the ME-catalyzed carboxylation of pyruvate with CO₂.