Equilibrium constants under physiological conditions for the condensation of acetaldehyde with tetrahydrofolic acid

Robert W. Guynn*, Linda B. Labaume, Jack Henkin

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    7 Scopus citations

    Abstract

    The nonenzymatic reaction of ethanol-derived CH3CHO with tissue constituents continues to be of interest as a potential mechanism underlying the toxicity of alcohol. The current study has focused on the spontaneous condensation of CH3CHO with H4folate under physiological conditions (38 °C, pH 7.0, I = 0.25 M). Computer analysis of uv spectral changes with increasing CH3CHO concentrations demonstrated the presence of at least two different adducts. The observed equilibrium constant (Kobs) for the formation of the first adduct is 91 ± 2 m-1 (121 ± 2 m-1 at 25 °C), a value which is unaffected by variations in ionic strength (0.06-1.0 m) or by free [Mg2+] up to 5 mm. The NMR spectrum is compatible with the structure: 5,10-CH3CH-H4folate analogous to the naturally occurring 5,10-CH2-H4folate. The formation of the latter compound from HCHO and H4folate, however, is much more favorable under the same conditions [Kobs = 3.0 ± 0.2 × 104 M-1 (38 °C), 3.6 ± 0.1 × 104 M-1 (25 °C)]. At the levels of CH3CHO which accumulate during ethanol metabolism in vivo only a small fraction of the H4folate will exist as the CH3CHO derivative, yet it may ultimately be the ratio of free CH3CHO to free HCHO in tissue which determines the physiological importance of the CH3CHO adduct. Other adduct(s) of CH3CHO with H4folate are observed at very high levels of CH3CHO but are unlikely to be of physiological significance.

    Original languageEnglish (US)
    Pages (from-to)181-190
    Number of pages10
    JournalArchives of biochemistry and biophysics
    Volume217
    Issue number1
    DOIs
    StatePublished - Aug 1982

    ASJC Scopus subject areas

    • Biophysics
    • Biochemistry
    • Molecular Biology

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