The alpha-form of S-adenosylmethionine synthetase isozymes from liver is principally functional

Treatment of rats with an ethionine plus adenine or a methionine diet leads not only to a marked increase of the alpha-form isozyme of S-adenosylmethionine synthetase in liver, but also to the accumulation of comparable amounts of S-adenosylethionine and S-adenosylmethionine in liver. Transplantation of ascites tumor cells into mice leads to a marked increase only of the beta-form isozyme in the host liver, but the levels of S-adenosylmethionine do not significantly change in liver.