The three-dimensional structure of glycosomal glyceraldehyde-3-phosphate dehydrogenase D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating), EC 1.12.1.12 from the sleeping-sickness parasite Trypanosoma brucei was solved by molecular replacement at 3.2-angstrom resolution with an X-ray data set collected by the Laue method. For data collection, three crystals were exposed to the polychromatic synchrotron X-ray beam for a total of 20.5 sec. The structure was solved by using the Bacillus stearothermophilus enzyme model Skarzynski, T., Moody, P. C. E. and Wonacott, A. J. (1987) J. Mol. Biol. 193, 171-187 with a partial data set which was 37% complete. The crystals contain six subunits per asymmetric unit, which allowed us to overcome the absence of 60% of the reflections by 6-fold density averaging. After molecular dynamics refinement, the current molecular model has an R factor of 17.6%. Comparing the structure of the trypanosome enzyme with that of the homologous human muscle enzyme, which was determined at 2.4-angstrom resolution, reveals important structural differences in the NAD binding region. These are of great interest for the design of specific inhibitors of the parasite enzyme