Inhibition by Ascorbate among Phosphofructokinase-1, Aldolase, Enolase, and Lactate Dehydrogenase in Rabbit Muscle

Anita Ricablanca; Ami Abbott; Fatimata Sonago; Montserrat Garcia; Rachel Primacio; Eric Patten; Mudassar Iqbal Arain; Eduardo Fricovsky

doi:10.5530/ijpi.2022.3.55

Anita Ricablanca Department of Medical Education, School of Medicine University of California, San Diego, La Jolla, CA 92093, USA
Ami Abbott Department of Medical Education, School of Medicine University of California, San Diego, La Jolla, CA 92093, USA.
Fatimata Sonago Department of Medical Education, School of Medicine University of California, San Diego, La Jolla, CA 92093, USA.
Montserrat Garcia Department of Medical Education, School of Medicine University of California, San Diego, La Jolla, CA 92093, USA.
Rachel Primacio Department of Medical Education, School of Medicine University of California, San Diego, La Jolla, CA 92093, USA.
Eric Patten Department of Medical Education, School of Medicine University of California, San Diego, La Jolla, CA 92093, USA.
Mudassar Iqbal Arain Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, La Jolla, CA, USA.
Eduardo Fricovsky Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, La Jolla, CA, USA.

DOI: https://doi.org/10.5530/ijpi.2022.3.55

Keywords: Phosphofructokinase-1, Aldolase, Enolase, Ascorbate, Rabbit.

Abstract

Background: These studies examined mutual protective relationships among rabbit muscle aldolase, enolase, phosphofructokinase-1 (PFK-1) and LDH from inhibitions by ascorbate (AA). It was proposed earlier that specific inhibitions of PFK-1 and LDH by AA faciltated glycogen storage in resting muscle by inhibiting glycolysis. Materials and Methods: The L-ascorbate (AA), L-ascorbyl dibutyrate (AADB), L-ascorbyl dipalmitate (AADP), L-ascorbyl palmitate (AAP), and L- ascorbyl stearate (AS) are shown in Figure 1 and were obtained from TCI and Alfa Aesar. Unless otherwise stated, all enzymes come from rabbit and all experimental temperatures were 25°C, pH 8.0. Results: Rabbit muscle enolase was examined for its protective effect on other rabbit muscle glycolytic enzymes against inhibitions by ascorbate (AA) and some AA-faty acid derivatives. The IC₅₀ values of enolase by ascorbate (AA) and IC₅₀values of AA-fatty acid derivatives were compared to estimate inhibition potency. For example, ascorbyl dipalmitate (AADP) was 156 times more inhibitory to enolase than AA. It was previously shown that rabbit muscle aldolase prevented LDH activity loses due to AA inhibition and prevented PFK-1 activity losses due both to dilution and AA inhibition; enolase was found to have the same effects as aldolase. Additionally, PFK-1 prevented enolase and LDH inhibitions by AA. LDH did not prevent enolase or PFK-1 from inhibition by AA. LDH did stimulate enolase activity but not PFK-1 activity. Conclusion: The results suggest that interactions among glycolytic enzyme serve to mutually protect one another from activity losses. The inhibition properties of the AA-fatty acid derivatives are discussed in relation to their possible roles in cancer and diabetes.

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