Mass spectrometric investigations on lactate adduction to equine myoglobin

Research focused on determining the fundamental mechanisms by which lactate influences color stability has not considered a direct effect of lactate on myoglobin. Thus, the objective of this study was to use Matrix Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry to examine lactate adduction to myoglobin. Equine oxymyoglobin and equine carboxymyoglobin (0.15 mM) were incubated with sodium lactate (200 mM) at 4 °C, pH 5.6 in 50 mM sodium citrate buffer or at 37 °C, pH 7.4 in 50 mM sodium phosphate buffer, simulating typical meat storage and physiological conditions, respectively. Controls consisted of myoglobin plus a volume of deionized water equivalent to that used to deliver the lactate treatments. No peaks corresponding to lactate-Mb adducts could be detected in the mass spectra of samples incubated up to 360 min at pH 7.4, 37 °C or 8 days at pH 5.6 and 4 °C. Our results suggest that lactate did not form covalent adducts with equine oxy- and carboxy-myoglobin.