An irreversible competitive inhibitor hydroxynaphthaldehyde phosphate was synthesized that is highly selective against the glycolytic enzyme fructose 1,6-bisphosphate aldolase from Trypanosoma brucei (causative agent of sleeping sickness). Inhibition involves Schiff base formation by the inhibitor aldehyde with Lys116 followed by reaction of the resultant Schiff base with a second residue. Molecular simulations indicate significantly greater molecular geometries conducive for nucleophilic attack in T. brucei aldolase than the mammalian isozyme and suggest Ser48 as the Schiff base modifying residue.