Methylthio group cleavage from methylthioadenosine. Description of an enzyme and its relationship to the methylthio requirement of certain cells in culture

Extracts of certain malignant murine hematopoietic cells are shown to contain an enzyme which catalyses the release of the methylthio group from methylthioadenosine. The enzyme is extractable from cells of five cell lines which grow well in vitro without addition of S-methylthio compounds (RSSCH 3). The enzyme activity is not present in cells of four lines which require methylthio groups for proliferation in vitro. The findings are consistent with the theory that the methylthio group is required in all dividing cells and that this group may be the essential product of the polyamine synthetic pathway.