L. Benov et I. Fridovich, Why superoxide imposes an aromatic amino acid auxotrophy on Escherichia coli - The transketolase connection, J BIOL CHEM, 274(7), 1999, pp. 4202-4206
The lack of superoxide dismutase and the consequent elevation of [O-2(-)] i
mposes, on Escherichia coli, auxotrophies far branched chain, sulfur-contai
ning, and aromatic amino acids. The former two classes of auxotrophies have
already been explained, whereas the third is explained herein. Thus O-2(-)
is shown to interfere with the production of erythrose-4-phosphate, which
is essential for the first step of the aromatic biosynthetic pathway. It do
es so by oxidizing the 1,2-dihydroxyethyl thiamine pyrophosphate; intermedi
ate of transketolase and inactivating this enzyme.