We report here the first crystal structure of a stable isosteric analogue of 1,3-bisphospho-D-glyceric acid (1,3-BPGA) bound to the catalytic domain of Trypanosoma cruzi glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH)in which the two phosphoryl moieties interact with Arg249. This complex possibly illustrates a step of the catalytic process by which Arg249 may induce compression of the product formed, allowing its expulsion fromthe active site.