A proteomic approach was used to identify a 39 kDa antigen of Paracoccidioides brasiliensis. Amino acid sequences of the N-terminal and of endoproteinase Lys-C digested peptides revealed the protein to be a fructose 1,6-biphosphate aldolase (FBA) Class II of P. brasiliensis. Two cDNA homologues, Pbfba1 and Pbfba2, were cloned and characterized. Pbfba1 encoded a predicted polypeptide of 360 amino acids that was highly homologous in the primary structure to the same enzyme from fungi and bacteria. The other DNA, Pbfba2, encoded a polypeptide predicted to be 363 amino acids. The sequence of Pbfba2 differed significantly from Pbfba1. Phylogenetic and molecular analysis supports the concept of gene duplication for FBAs in P. brasiliensis, constituting a two-member family. Expression analysis demonstrated differential expression for both fbas genes in P. brasiliensis cells.