Development of a Standardized MRM Method for the Quantification of One Carbon Metabolism Enzymes.

One-carbon metabolism (1CM) plays a central role in liver physiology, being the source of essential metabolites such as S-adenosylmethionine, the main alkylating agent in living cells, and glutathione, their most important nonenzymatic antioxidant defense. Impairment of 1CM in hepatocytes is a recognized factor associated to chronic liver disorders and hepatocellular carcinoma. With this in mind, we have proposed the concept of functional biomarker referring to a cellular pathway that can be systematically monitored as indicative of a particular physiological or pathological condition. Here we describe a targeted mass spectrometry (MRM) protocol to simultaneously quantify 13 1CM enzymes in liver tissue specimens.