LACTATE-DEHYDROGENASE FROM THE PROTOZOAN PARASITE, TRICHOMONAS-VAGINALIS

Lactate dehydrogenase (LDH) has been purified to near homogeneity from the parasitic protozoan, Trichomonas vaginalis, using ion exchange an d affinity chromatographies. Two distinct peaks (P1 and P2) of LDH act ivity were eluted. from DEAE-Sepharose, and LDH from each peak was pur ified separately. LDH from both peaks exhibited identical apparent sub unit molecular weights of 39 kDa, as judged from SDS-PAGE and focused as single spots with identical pIs during 2D gel electrophoresis. In a ddition, activity staining for LDH activity on non-denaturing polyacry lamide gels oi the crude homogenate yielded a single tight doublet, wh ich was identical to the pattern seen when either P1 or P2 were analyz ed under similar conditions. P1 and P2 exhibited dramatically differen t apparent K(m)s for pyruvate and lactate, but neither was affected by ATP, ADP, citrate, succinate, or fructose-1,6-diphosphate when assaye d at near K-m concentrations of pyruvate. In contrast to mammalian LDH s, the trichomonad enzyme could use 3-acetylypyridine NAD(+) as a subs trate. Copyright (C) 1996 Elsevier Science Inc.