Malate dehydrogenase (EC 1.1,1,37.) (MDH) was purified to apparent homogeneity from the cytosolic fraction of the protozoan Trichomonas vaginalis Donné. The four step purification included ion-exchange chromatography (DEAE-Sephacel and Q-Sepharose, elution with NaCl) and affinity chromatography (Reactive Red Agarose, elution with NADH and NaCl). The enzyme was purified about 132-fold (30.6% yield) to a specific activity of 352 units mg~'. The Km values determined at pH 7.8 (pH optimum from 7.5 to 8.3) for oxaloacetate and NADH were 16.2 pM and 10.6 μΜ, respectively. The MDH activity was inhibited by the substrate, decreasing to 50% at about 1 mM concentration of oxaloacetate. The reverse reaction from malate to oxaloacetate showed a pH optimum around pH 9.5. The Km for malate and NAD* (determined at pH 7.8) were 1220 pM and 69.9 pM, respectively. SDS-PAGE analysis of the purified MDH revealed a single band with an apparent size of 34.5 kDa. The native molecular weight was estimated by HPLC gel filtration to be 60 kDa, which indicates that the T. vaginalis MDH exists as a dimer.
Seven of 12 lacertid lizards Acanthodactylus boskianus (Daiidin, 1802), passed oocysts of an Isospora species. Comparison with other species of the genus Isospora Schneider, 1881 indicated that found coccidium represented a new species, for which the name /. abdallahi is proposed. Sporulated oocysts of /. abdallahi are spherical or subspherical, 25.8 (24.5-29.0) x 23.9 (23.0-25.5) pm, shape index (length/width) being 1.07 (1.00-1.16), with a smooth, bilayered oocyst wall that is slightly yellowish, about 2 pm thick. Micropyle, oocyst residuum and polar granule are absent. Sporocysts are ovoidal, 15.4 (14.0-16.0 x 9.4 (9.0-10.0) pm, with smooth and colorless sporocyst wall, shape index 1.6 (1.5-1.8). Stieda body is dome-like, substieda body spherical to subspherical. Sporocyst residuum is composed of numerous granules of different size, scattered among sporozoites. Most oocysts are passed unsporulated; sporulation was completed within 12 h at 25'C. Endogenous development occurs inside nuclei of enterocytes in the small intestine.