ANALYTICAL PROCEDURE FOR DETERMINATION OF S-ADENOSYLMETHIONINE, S-ADENOSYLHOMOCYSTEINE, AND S-ADENOSYLETHIONINE IN SAME ISOCRATIC HPLC RUN,WITH A PROCEDURE FOR PREPARATION AND ANALYSIS OF THE ANALOG S-ADENOSYLHOMOCYSTEINE SULFOXIDE

Virtually all methyltransferase enzymes are regulated largely by the r elative levels of S-adenosylmethionine (SAM) to its metabolic product, S-adenosylhomocysteine (SAH). Ethionine is the hepatocarcinogenic ant imetabolite of methionine, and has been found to produce hypomethylati on of hepatic DNA when fed to rats in acute doses. The hypomethylation apparently results from the accumulation in the liver of S-adenosylet hionine (SAE), the sulfur activation product of ethionine, which is a competitive inhibitor of DNA methylase. Researchers seeking to measure SAM and SAH levels by HPLC in the past have experienced numerous anal ytical problems because of their separation characteristics. Previous methods have either required two separate HPLC runs or used gradient e lution to measure the two compounds. The method outlined here, is an a ccurate and precise method, that measures SAM and SAH as well as SAE i n a single isocratic HPLC run. S-Adenosyl-l-homocysteine sulfoxide (SA HO), the sulfoxide of SAH is known to be formed by spontaneous oxidati on of SAH during sample preparation and storage. We have prepared the SAHO using a 4 hour process. Since SAHO is not readily available comme rcially, the present method could be very beneficial to researchers wh o need to verify whether SAH oxidation has occurred in analytical samp les, or whether oxidation of the SAH has occurred in tissues.