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[Mechanism of a decrease of inducibility of tyrosine aminotransferase by carcinogenic aminoazo dyes. Absence of

N P Zakharova, T T Glazko, V I Kaledin

    Biokhimiia (Moscow, Russia)
    |February 1, 1980
    PubMed

    Insights

    o-aminoazotoluene (OAT) does not directly affect tyrosine aminotransferase (TAT) activity. This cancerogen also does not indirectly influence TAT through phosphorylation or dephosphorylation systems, indicating other mechanisms for its effects in vivo.

    Area of Science:

    • Biochemistry
    • Enzymology
    • Toxicology

    Context:

    • Investigating the interaction between carcinogens and key metabolic enzymes.
    • Understanding the molecular mechanisms of carcinogen-induced changes in enzyme activity.
    • Focusing on tyrosine aminotransferase (TAT) in mouse liver cytosol.

    Purpose:

    • To determine the effect of o-aminoazotoluene (OAT) on tyrosine aminotransferase (TAT) activity.
    • To examine if OAT influences TAT activity directly or indirectly via metabolic activation and phosphorylation/dephosphorylation systems.
    • To elucidate the mechanism behind OAT's observed reduction of TAT induction by hydrocortisone in vivo.

    Summary:

    • Incubation of mouse liver cytosol with o-aminoazotoluene (OAT) in the presence of metabolic activation systems (liver microsomes and NADPH2) and dephosphorylation systems (light mitochondria and ATP) showed no direct or indirect effect on tyrosine aminotransferase (TAT) activity.
    • The study demonstrated that OAT does not alter TAT enzyme activity through direct interaction or by modulating the phosphorylation-dephosphorylation pathways.
    • These findings suggest that the previously observed decrease in TAT induction by hydrocortisone in mice treated with OAT is not caused by a direct impact of the carcinogen on the enzyme itself.

    Impact:

    • Provides crucial insights into the non-enzymatic mechanism of carcinogen action.
    • Clarifies the role of OAT in modulating hepatic enzyme activity, specifically TAT.
    • Contributes to understanding the complex interplay between environmental toxins and cellular metabolic regulation.

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