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 reduct ase from Trypanosoma cruzi were measured for a series of N-substituted-L-cy steinylglycyl-3-dimethylaminopropylamides, in which the cysteine N-substitu ent was either a variant of the benzyloxycarbonyl group or was L-phenylalan ine 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- an d 10-fold, respectively. Similarly, relative to the carbobenzoxy group, an N-L-phenylalanyl or N-L-tryptophanyl replacement on the cysteine hardly alt ered k(cat), but increased K-m values by 16.6 and 7.4 fold, respectively. T hese observations were consistent with the K-m values referring primarily t o binding for this series of nonspecific substrates.