Abstract
SUMMARY: Regulation of the cross-pathway type was found in Aspergillus nidulans. Ornithine carbamoyltransferase, a biosynthetic enzyme of the arginine pathway, is derepressed as a result of deprivation not only of arginine but also of histidine, proline and tryptophan. Cross-pathway regulation operates in the mutant suD19 in which the ornithine carbamoyl-transferase level is insensitive to arginine. The spectrum of the amino acids involved in this type of regulation seems to be different from those described for other fungi.