Kinetic mechanism of fuculose-1-phosphate aldolase from the hyperthermophilic Archaeon Methanococcus jannaschii

Fuculose-1-phosphate aldolase (FucA) is a useful biocatalyst with potential applications in chiral synthesis. In this study, the overall kinetic mechanism of FucA from the archaeon Methanococcus jannaschii was studied. The Km values of dihydroxyacetone phosphate (DHAP) and dl-glyceraldehyde were 0.09 and 0.74 mM, respectively. Dead-end inhibition by trimethyl phosphonoacetate and dl-threose were competitive and uncompetitive with respect to DHAP and dl-glyceraldehyde. Inhibition patterns obtained using reaction products were noncompetitive vs. DHAP and competitive vs. dl-glyceraldehyde. The equilibrium constant was 8.309 × 10−3 M as assessed by varying the [DHAP]/[product] ratio at a fixed dl-glyceraldehyde concentration and by measuring the change in DHAP concentration after equilibrium was reached. This constant is consistent with the Keq value obtained from 13C NMR (15.625 × 10−3 M). The resultant inhibition kinetics may suggest the insights of kinetic mechanism of the FucA catalyzed reaction.