ABSTRACT
AdoMet is a high energy compound and is quite unstable in aqueous buffers at physiologi cal conditions (half life of AdoMet at pH 7.5 and 37 °C is in the order of 10-20 h).29 It readily decomposes in aqueous solutions at pH > 6 to form adenine and 5-ribosylmethionine. At moderately acid milieu (2 < pH < 6), an intramolecular attack o f the carboxylate group onto the y-carbon o f the methionine moiety leads to 5'-deoxy-5'-methylthioadenosine and homoserine lactone. The third decomposition pathway is pH-independent and leads to epimerization o f the chiral sulfonium center. Therefore long term storage o f AdoMet preparations is possible only in acidic buffers (pH 2-3.5) and at low temperatures (-20 or -70° C). Other general precautions such as storing AdoMet in crystalline form or avoiding multiple cycles o f freezing-thawing of stock solutions are advised.
