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.