5′-methylthioadenosine and related compounds as precursors of S-adenosylmethionine in yeast

A supplement of 5′-methylthioadenosine (1.0 mM) in the culture medium of the yeast Candida utilis doubled the intracellular level of S-adenosylmethionine. 70% of the specific radioactivity of 8-¹⁴C]adenine- or ³⁵S-labeled 5′-methylthioadenosine was recovered in S-adenosylmethionine. The possibility of incorporation of the unfragmented nucleoside was tested by dilution experiments. An additional supplement of adenine or l-methionine greatly reduced the isotope recovery in the sulfonium compound; degradation of the nucleoside is thus indicated as the first phase of the recycling process.