The phosphothreonine lyase class of enzymes represents a recently discovered set of enzymes that catalyze a dephosphorylation reaction. The catalysis is carried out using a unique elimination mechanism without any involvement of cofactors. Crystallographic studies of SpvC, a phosphothreonine lyase, and its mutant show that the mutation of the general catalytic acid does not result in any significant perturbations to the tertiary and the secondary structure of the protein. Using results from the structural studies and a deuterium isotope exchange experiment, we conclude that the reaction catalyzed by SpvC may not involve formation of a carbanion at the active site.