Purification of Fumarase from Corynebacterium glutamicum andInhibition by Substrate Analogs

Fumarase (EC 4.2.1.2) from Corynebacterium glutamicum (Breuibacterium flavum) ATCC 14067 was purified to homogeneity. Its amino-terminal sequence (residues 1 to 30) corresponded to the sequence (residues 6 to 35) of the deduced product of the fumarase gene of C. glutamicum (GeneBank accession no. BAB98403) . The molecular mass of the native enzyme was 200 kDa. The protein was a homotetramer, with a 50-kDa subunit molecular mass. The homotetrameric and stable properties indicated that the enzyme belongs to a family of Class II fumarase. Equilibrium constants (Keq) for the enzyme reaction were determined at pH 6.0, 7.0, and 8.0, resulting in Keq = 6.4, 6.1, and 4.6 in phosphate buffer, while 16, 19, and 17 in the non-phosphate buffers, respectively. Among amino acids and nucleotides tested ATP inhibited the enzyme. Substrate analogs, meso-tartrate, D-tartrate, and pyromellitate, inhibited the enzyme competitively, and D-malate in mixed-type.