Prospettive nell'applicazione della misura di amminoacidi metilati quali bioindicatori di attività prolifertaiva cellulare

Methylated amino acids as prospective biomarkers of cell prolipheration. S-methylcysteine (SMC) is a minor amino acid naturally excreted in human urine, a protective agent against oxidative stress and a biotransformation product of the fumigant biocide methyl bromide and of nicotine. A metabolic source of SMC is the catabolism of a repair catalytic protein (MGMT; EC 2.1.1.37) which is able to specifically remove the methyl group from the modified DNA nucleotide O-6-methyl-guanine to revert the normal GC base pairing. To assess the value of SMC as a candidate biomarker of proliferative phenomena a sensitive analytical method by GC-MS was applied to measure SMC in a pilot study of healthy subjects to preliminarily assess the magnitude and the extent of intra- and inter-individual variability of its urinary elimination. Levels in the morning urine of 3 healthy fertile-age women followed for one month are in the 20-700 μg/L range (n=61) with large inter-day and inter-individual variations, little apparent regular monthly cycle and no mutual synchronization. In a young healthy male urine samples taken throughout a few days yielded concentrations in the same 90-810 μg/L range (n=11), with no apparent circadian cycle. This preliminary results points at SMC as a candidate biomarker for the study of methylation turnover in several biochemical processes.