Evidence for the co-existence of glutathione reductase and trypanothione reductase in the non-trypanosomatid Euglenozoa:: Euglena gracilis Z.

Two NADPH-dependent disulfide reductases, glutathione reductase and trypanothione reductase, were shown to be present in Euglena gracilis, purified to homogeneity and characterized, The glutathione reductase (M-r 50 kDa) displays a high specificity towards glutathione disulfide with a K-M of 54 mu M. The amino acid sequences of two peptides derived from the trypanothione reductase (M-r 54 kDa) show a high level of identity (81% and 64%) with sequences of trypanothione reductases from trypanosomatids. The trypanothione reductase is able to efficiently reduce trypanothione disulfide (K-M 30.5 mu M) and glutathionylspermidine disulfide (K-M 90.6 mu M) but not glutathione disulfide, nor Escherichia coli thioredoxin disulfide, nor 5,5'-dithiobis(2-nitrobenzoate) (DTNB). These results demonstrate for the first time (i) the existence of trypanothione reductase in a non-trypanosomatid organism and (ii) the coexistence of trypanothione reductase and glutathione reductase in E. gracilis. (C) 1999 Federation of European Biochemical Societies.