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Leishmaniasis is a spectrum of conditions caused by infection with the protozoan Leishmania spp. parasites. Leishmaniasis is endemic in 98 countries around the world, and resistance to current anti-leishmanial drugs is rising. Our work has identified and characterised a previously unstudied galactokinase-like protein (GalK) in Leishmania donovani , which catalyses the MgATP-dependent phosphorylation of the C-1 hydroxyl group of d -galactose to galactose-1-phosphate. Here, we report the production of the catalytically active recombinant protein in E. coli , determination of its substrate specificity and kinetic constants, as well as analysis of its molecular envelope using in solution X-ray scattering. Our results reveal kinetic parameters in range with other galactokinases with an average apparent Km value of 76 μM for galactose, V max and apparent K cat values with 4.46376 × 10−9 M/s and 0.021 s−1, respectively. Substantial substrate promiscuity was observed, with galactose being the preferred substrate, followed by mannose, fructose and GalNAc. Ld GalK has a highly flexible protein structure suggestive of multiple conformational states in solution, which may be the key to its substrate promiscuity. Our data presents novel insights into the galactose salvaging pathway in Leishmania and positions this protein as a potential target for the development of pharmaceuticals seeking to interfere with parasite substrate metabolism. • Galactose, mannose, fructose and GalNAc are substrates for Ld GalK. • Kinetic parameters are in range with other galactokinases. • Structural flexibility indicates conformational changes upon ligand binding. • Development of anti-leishmanial therapeutics exploiting galactose metabolism. [ABSTRACT FROM AUTHOR]