The unusual transhydrogenase of Entamoeba histolytica

We have expressed and purified a protein fragment from Entamoeba histolytic a. It catalyses transhydrogenation between analogues of NAD(H) and NADP(H). The characteristics of this reaction resemble those of the reaction cataly sed by a complex of the NAD(H)- and NADP(H)-binding subunits of proton-tran slocating transhydrogenases from bacteria and mammals. It is concluded that the complete En. histolytica protein, which, along with similar proteins f rom other protozoan parasites, has an unusual subunit organisation, is also a proton-translocating transhydrogenase. The function of the transhydrogen ase, thought to be located in organelles which do not have the enzymes of o xidative phosphorylation, is not clear. (C) 2001 Federation of European Bio chemical Societies. Published by Elsevier Science B.V. All rights reserved.