Accumulation of S-Sulphocysteine by a Mutant Strain of Aspergillus nidulans

Abstract

RECENT work in this laboratory^1,2, together with earlier observations by Hockenhull³, have provided strong evidence indicating that in Aspergillus nidulans cysteine is synthesized from inorganic sulphur sources via S-sulphocysteine (cysteine-S-sulphonate) as the immediate precursor. This latter compound has, however, not yet been reported to occur in micro-organisms. In the present communication we report that a mutant strain of A. nidulans actually accumulates radioactive S-sulphocysteine when grown in a medium containing sulphate labelled with sulphur-35. The mutant used, strain 793, has been shown to be genetically blocked in the reaction by which S-sulphocysteine is converted to cysteine^1,2.