Maleic Acid is a Glutamate Decarboxylase (GAD) inhibitor of E. coli and L. monocytogenes. Human Endogenous Metabolite GAD
The MICs of WT 10403S for the acids (e.g., Maleic Acid) are 34 mM, 25 mM, 31 mM and 30 mM which correspond to pH values prior to growth of 4.84, 5.14, 5.32 and 5.02 respectively. Of all compounds tested, Maleic Acid is the least inhibitory despite acting at a lower pH (4.84). The most acid resistant (10403S) and the weakest (EGD-e) strain are challenged with 8.6 mM and 4.3 mM of each organic acid at pH 3 and 3.3 respectively. On both strains, Maleic Acid is the most bactericidal[2].
[1]. Fonda ML, et al. Glutamate decarboxylase. Substrate specificity and inhibition by carboxylic acids. Biochemistry. 1972 Mar 28;11(7):1304-9. [2]. Paudyal R, et al. A novel approach in acidic disinfection through inhibition of acid resistance mechanisms; Maleic acid-mediated inhibition of glutamate decarboxylase activity enhances acid sensitivity of Listeria monocytogenes. Food Microbiol. 2018 Feb;69:96-104.