S-Adenosylmethionine metabolism by members of the genus Candida

Abstract

S-Adenosylmethionine and S-methylmethionine: homocysteine methyltransferase activity was measured in cell-free extracts from seven different species (15 strains) of the genus Candida. All strains were able to form methionine via a transmethylation reaction with S-adenosylmethionine and homocysteine. However, some strains were not able to use S-methylmethionine as a methyl donor. Cell-free extracts from two strains of C. guilliermondii formed no methionine when S-methylmethionine was the methyl donor and one strain (C. guilliermondii, CDC) showed methionine-forming activity with S-adenosylmethionine and homocysteine only when the growth medium was supplemented with L-methionine. In general, greater methyltransferase activity was observed in the cell-free extracts from the more pathogenic members of the genus (i.e., C. albicans and C. tropicalis). Supplementation of the growth medium with L-methionine induced homocysteine methyltransferase activity. Ten of the 15 strains had the capacity to synthesize and store S-adenosylmethionine in their vacuole and all 15 strains had S-adenosylmethionine-degrading enzymes. The activity of the latter enzyme was not increased when cells were grown in L-methionine-supplemented medium.