Evidence for an interrelation in the metabolism of lysine, arginine and pyrimidines in Neurospora

Abstract

The behavior of a strain of Neurospora crassa carrying the pyrimidineless gene 3a (37301) and s, a second mutant gene which suppresses the effect of 3a, has been described briefly in an earlier publication.(1) A strain carrying 3a alone has an absolute requirement for pyrimidine, while 3a-s reaches about one-half the maximum growth of the wild type on the un-supplemented basal medium.(2) However, if arginine is present in this medium the pyrimidine requirement is again manifested. The effect of arginine may be suppressed in turn by the addition of lysine. This response to arginine and lysine suggested the possibility that one or both of these amino acids are involved in the biosynthesis of pyrimidines. More recent investigations have provided evidence that a relationship does exist, but its nature is not yet understood.