Lysine-146 of rabbit muscle aldolase is essential for cleavage and condensation of the C3-C4 bond of fructose 1,6-bis(phosphate)

Site-directed mutagenesis to substitute lysine-146 with leucine, alanine, histidine or glutamine and to produce mutant protein forms in rabbit muscle aldolase reveals that lysine-146 is essential for the chemical phase of catalysis and C3-C4 bond cleavage and its absence affects both processes. The substrate cleavage rates of the mutant enzymes is less than the standard values and their Schiff base formation rates are also low. The enzymes catalyze the release of carbanion intermediates but affect the rate of C3-C4 bond cleavage, confirming that lysine-146 is the key component of catalysis.