Synthesis and enzymology of modified N-benzyloxycarbonyl-L-cysteinylglycyl-3,3-dimethylaminopropylamide disulphides as alternative substrates for trypanothione reductase from Trypanosoma cruzi: Part 3

Kinetic data for alternative substrates of recombinant trypanothione reductase from Trypanosoma cruzi were measured for a series of N-substituted-L-cysteinylglycyl-3-dimethylaminopropylamides, in which the cysteine N-substituent was either a variant of the benzyloxycarbonyl group or was L-phenylalanine or L-tryptophan. Replacing the benzylic ether oxygen atom by CH₂ or NH had relatively minor effects on k_cat, but raised the value of K_m 4.5- and 10-fold, respectively. Similarly, relative to the carbobenzoxy group, an N-L-phenylalanyl or N-L-tryptophanyl replacement on the cysteine hardly altered k_cat, but increased K_m values by 16.6 and 7.4 fold, respectively. These observations were consistent with the K_m values referring primarily to binding for this series of nonspecific substrates.