Accumulation of S-sulphocysteine by a mutant strain of Aspergillus nidulans.

Abstract

RECENT work in this laboratory1,2, 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 cysteine1,2.