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  • Atomic, Molecular and Optical Physics  (2)
  • 4-Hydroxyphenylacetate  (1)
  • 2020-2021
  • 1990-1994  (3)
  • 1960-1964
Collection
Publisher
Years
  • 2020-2021
  • 1990-1994  (3)
  • 1960-1964
Year
  • 1
    ISSN: 1432-072X
    Keywords: Phenylacetate ; 4-Hydroxyphenylacetate ; Phenylglyoxylate ; Alpha-Oxidation ; Pseudomonas ; Oxidoreductase ; CoA ligase ; Benzoyl-CoA ; Anaerobic aromatic metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anaerobic degradation of (4-hydroxy)phenylacetate in denitrifying Pseudomonas sp. was investigated. Evidence is presented for α-oxidation of the coenzyme A (CoA)-activated carboxymethyl side chain, a reaction which has not been described. The C6−C2 compounds are degraded to benzoyl-CoA and furtheron to CO2 via the following intermediates: Phenylacetyl-CoA, phenylglyoxylate, benzoyl-CoA plus CO2; 4-hydroxyphenylacetyl-CoA, 4-hydroxyphenylglyoxylate, 4-hydroxybenzoyl-CoA plus CO2, benzoyl-CoA. Trace amounts of mandelate possibly derived from mandelyl-CoA were detected during phenylacetate degradation in vitro. The reactions are catalyzed by (i) phenylacetate-CoA ligase which converts phenylacetate to phenylacetyl-CoA and by a second enzyme for 4-hydroxyphenylacetate; (ii) a (4-hydroxy)-phenylacetyl-CoA dehydrogenase system which oxidizes phenylacetyl-CoA to (4-hydroxy)phenylglyoxylate plus CoA; and (iii) (4-hydroxy)phenylglyoxylate: acceptor oxidoreductase (CoA acylating) which catalyzes the oxidative decarboxylation of (4-hydroxy)phenylglyoxylate to (4-hydroxy)benzoyl-CoA and CO2. (iv) The degradation of 4-hydroxyphenylacetate in addition requires the reductive dehydroxylation of 4-hydroxybenzoyl-CoA to benzoyl-CoA, catalyzed by 4-hydroxybenzoyl-CoA reductase (dehydroxylating). The whole cell regulation of these enzyme activities supports the proposed pathway. An ionic mechanism for anaerobic α-oxidation of the CoA-activated carboxymethyl side chain is proposed. Phenylacetic acids are plant constituents and in addition are formed from a large variety of natural aromatic compounds by microorganisms; their degradation therefore plays a significant role in nature, as illustrated in the preceding paper (Mohamed and Fuchs 1993). We have investigated and purified an enzyme which catalyzes the first step in the anaerobic degradation of phenylacetate in a denitrifying Pseudomonas sp. Phenylacetate is converted to phenylacetyl-CoA by phenylacetate-CoA ligase (AMP forming). The postulated function of this enzyme is corroborated by the strict regulation of its expression. 4-Hydroxyphenylacetate appears to be similarly activated by an independent enzyme prior to further degradation. We have suggested before that phenylacetyl-CoA is anaerobically converted by α-oxidation of the side chain to phenylglyoxylate1, which is oxidatively decarboxylated to benzoyl-CoA plus CO2 (Seyfried et al. 1991; Dangel et al. 1991). 4-Hydroxyphenylacetate was proposed to be similarly oxidized to 4-hydroxybenzoyl-CoA plus CO2, followed by reductive dehydroxylation to benzoyl-CoA. The evidence was not presented in full, and the crucial α-oxidation was not demonstrated in vitro. We present here ample evidence for this pathway. A hypothetical mechanism is proposed by which the oxidation of the α-methylene group to an α-carbonyl group may occur.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 461-486 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study is a unified approach to quantum theories of polyacen carcinogenesis. Part I discusses the M, L, and B regions theory. Although the M region of polyacens is much less reactive than is the K region, the chemical reactivity of these two regions parallels each other. Consequently, the K-L Pullman's theory may be reformulated by replacing the K region by the M region. The M-L regions theory improves all the quantum structure-carcinogenic activity relationships obtained previously in the K-L framework. Moreover, it would appear that in these correlations, the most important role is played by nonconcerted electrophilic reactions. We suggest that the M-L modified Pullman's theory and the Bay (B) region theory, proposed by Jerina et al., are related to different steps of the metabolic activation mechanism leading to ultimate carcinogen: the first step for the Pullman's theory and the carbocation step for the theory of the Bay region. We have termed the “M, L and B regions theory” as this unified approach to the problem of polyacens carcinogenesis.
    Additional Material: 8 Ill.
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  • 3
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study is a unified approach to quantum theories of polyacen carcinogenesis. Part II is on the role of the K-region in metabolic activation process leading to ultimate carcinogen and discusses the M, L, and BK theory. The saturation of the polyacen K-region, or the transformation into a quinoid one, deactivates the carcinogenic process going through a diol epoxyde, which results in Bay-region carbocation. K and B regions must be considered as two interdependent parts of the same structural entity, which may be termed the BK-region. The M, L, and BK theory achieves a complete unification of the Pullman and Jerina and other theories.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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