TY  - JOUR
AU  - Gabriel, F. L. P.
AU  - Cyris, M.
AU  - Jonkers, N.
AU  - Giger, W.
AU  - Günther, K.
AU  - Kohler, H.-P. E.
TI  - Elucidation of the ipso-substitution mechanism for side-chain cleavage of alpha-quaternary 4-nonylphenols and 4-t-butoxyphenol in Sphingobium xenophagum Bayram
JO  - Applied and environmental microbiology
VL  - 73
SN  - 0099-2240
CY  - Washington, DC [u.a.]
PB  - Soc.
M1  - PreJuSER-56261
SP  - 3320 - 3326
PY  - 2007
N1  - Record converted from VDB: 12.11.2012
AB  - Recently we showed that degradation of several nonylphenol isomers with alpha-quaternary carbon atoms is initiated by ipso-hydroxylation in Sphingobium xenophagum Bayram (F. L. P. Gabriel, A. Heidlberger, D. Rentsch, W. Giger, K. Guenther, and H.-P. E. Kohler, J. Biol. Chem. 280:15526-15533, 2005). Here, we demonstrate with 18O-labeling experiments that the ipso-hydroxy group was derived from molecular oxygen and that, in the major pathway for cleavage of the alkyl moiety, the resulting nonanol metabolite contained an oxygen atom originating from water and not from the ipso-hydroxy group, as was previously assumed. Our results clearly show that the alkyl cation derived from the alpha-quaternary nonylphenol 4-(1-ethyl-1,4-dimethyl-pentyl)-phenol through ipso-hydroxylation and subsequent dissociation of the 4-alkyl-4-hydroxy-cyclohexadienone intermediate preferentially combines with a molecule of water to yield the corresponding alcohol and hydroquinone. However, the metabolism of certain alpha,alpha-dimethyl-substituted nonylphenols appears to also involve a reaction of the cation with the ipso-hydroxy group to form the corresponding 4-alkoxyphenols. Growth, oxygen uptake, and 18O-labeling experiments clearly indicate that strain Bayram metabolized 4-t-butoxyphenol by ipso-hydroxylation to a hemiketal followed by spontaneous dissociation to the corresponding alcohol and p-quinone. Hydroquinone effected high oxygen uptake in assays with induced resting cells as well as in assays with cell extracts. This further corroborates the role of hydroquinone as the ring cleavage intermediate during degradation of 4-nonylphenols and 4-alkoxyphenols.
KW  - Biodegradation, Environmental
KW  - Cyclohexanes: metabolism
KW  - Cyclohexenes
KW  - Gas Chromatography-Mass Spectrometry
KW  - Metabolic Networks and Pathways
KW  - Molecular Structure
KW  - Oxygen: metabolism
KW  - Oxygen Isotopes: metabolism
KW  - Phenols: metabolism
KW  - Sphingomonas: chemistry
KW  - Sphingomonas: growth & development
KW  - Sphingomonas: metabolism
KW  - Cyclohexanes (NLM Chemicals)
KW  - Cyclohexenes (NLM Chemicals)
KW  - Oxygen Isotopes (NLM Chemicals)
KW  - Phenols (NLM Chemicals)
KW  - cyclohexadienone (NLM Chemicals)
KW  - 4-nonylphenol (NLM Chemicals)
KW  - 4-butoxyphenol (NLM Chemicals)
KW  - Oxygen (NLM Chemicals)
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
C6  - pmid:17369338
C2  - pmc:PMC1907130
UR  - <Go to ISI:>//WOS:000246680500024
DO  - DOI:10.1128/AEM.02994-06
UR  - https://juser.fz-juelich.de/record/56261
ER  -