Аннотация
Hydroxylamino aromatic compounds are converted to either the corresponding
aminophenols or protocatechuate during the bacterial degradation
of nitroaromatic compounds. The origin of the hydroxyl group of
the products could be the substrate itself (intramolecular transfer
mechanism) or the solvent water (intermolecular transfer mechanism).
The conversion of hydroxylaminobenzene to 2-aminophenol catalyzed
by a mutase from Pseudomonas pseudoalcaligenes JS45 proceeds by
an intramolecular hydroxyl transfer. The conversions of hydroxylaminobenzene
to 2- and 4-aminophenol by a mutase from Ralstonia eutropha JMP134
and to 4-hydroxylaminobenzoate to protocatechuate by a lyase from
Comamonas acidovorans NBA-10 and Pseudomonas sp. strain 4NT were
proposed, but not experimentally proved, to proceed by the intermolecular
transfer mechanism. GC-MS analysis of the reaction products formed
in H(2)(18)O did not indicate any (18)O-label incorporation during
the conversion of hydroxylaminobenzene to 2- and 4-aminophenols
catalyzed by the mutase from R. eutropha JMP134. During the conversion
of 4-hydroxylaminobenzoate catalyzed by the hydroxylaminolyase from
Pseudomonas sp. strain 4NT, only one of the two hydroxyl groups
in the product, protocatechuate, was (18)O labeled. The other hydroxyl
group in the product must have come from the substrate. The mutase
in strain JS45 converted 4-hydroxylaminobenzoate to 4-amino-3-hydroxybenzoate,
and the lyase in Pseudomonas strain 4NT converted hydroxylaminobenzene
to aniline and 2-aminophenol but not to catechol. The results indicate
that all three types of enzyme-catalyzed rearrangements of hydroxylamino
aromatic compounds proceed via intramolecular transfer of hydroxyl
groups.
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