Abstract

S-adenosyl-L-methionine (SAM) is the main biological methyl donor in transmethylation reactions, consisting in the transferring of a methyl moiety to different substrates including DNA, proteins, lipids and RNA. SAM level in the organism decreases with aging and restoring the original levels through exogenous supplementation is an important tool for the improvement of many vital functions. Indeed, SAM deficiency may contribute to the onset of several diseases, i.e. depression, liver diseases, osteoarthritis and senile neurological disorders such as Alzheimer’s and Parkinson’s diseases. Recent evidences indicate that SAM may have an involvement in oxidative stress, a process which typically involves an alteration of cellular sulfur amino acids homeostasis. SAM is not only the principal methyl donor, but also a precursor of glutathione, the major endogenous antioxidant, whose role in counteracting oxidative stress is well known. In this review we will highlight the role of SAM not just as a methyl-donor but also as a regulator of different metabolic pathways involved in the antioxidant response in brain related disorders.