Adenosine analogs as substrates and inhibitors of S-adenosylhomocysteine hydrolase in intact lymphocytes

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Abstract
A number of adenosine analogues were examined for their ability to interact with S-adenosyl-L- homocysteine (SAH) hydrolase in intact mouse lymphocytes. In the presence of erythro-9-(2-hydroxy-3-nonyl)adenine, 3-deazaadenosine, 8-azaadenosine, formycin A, 2-aminoadenosine, 2-fluoradenosine, N6-methyladenosine, N6-hydroxyadenosine, purine ribonucleoside and inosine were each metabolized to radioactive analogues of SAH when cells were labeled with either L-[23H]methionine or L-[35S]homocysteine. Tubercidin was shown to undergo metabolism to S-[3H]tubercidinyl-L-methionine and to S-[3H]tubercidinyl-L-homocysteine in cells labeled with [2-3H]methionine. 9-.beta.-D-Arabinofuranosyladenine and 2''-deoxyadenosine caused marked elevations of [3H]SAH in cells preloaded with [2-3H]methionine but were not themselves metabolized detectably to SAH analogues. Adenine and 5''-deoxyadenosine caused substantial elevations of [3H]SAH under these same conditions. Some of the adenosine analogues metabolized to SAH analogues also caused an elevation SAH in the lymphocytes. The potential of adenosine analogues to interfere with cellular methylation reactions due either to their inhibition of SAH hydrolase or to their metabolism, via this enzyme, to SAH analogues was indicated.