An asparaginase of Aspergillus nidulans is subject to oxygen repression in addition to nitrogen metabolite repression

Abstract

Of five amidohydrolase activities subject to nitrogen metabolite repression in Aspergillus nidulans, L-asparaginase shows clearest evidence of also being subject to repression by atmospheric oxygen. Such oxygen repressibility is only evident under nitrogen metabolite derepressed conditions. Asparaginase levels are also considerably elevated by areA300, an altered function allele of the positive acting wide domain regulatory gene areA mediating nitrogen metabolite repression and are drastically reduced by loss of function mutations in areA. A. nidulans has two L-asparaginase enzymes and it has been shown by the use of appropriate mutants that these regulatory effects are exerted on the expression of that specified by the ahrA gene but probably not that specified by the apnA gene.

The Molecular Genetics of Nitrate Assimilation in Fungi and Plants

“…Probably the most extraordinary areA mutation is areA300, which not only leads to nitrogen metabolite derepression of several activities, including nitrate and nitrite reductases, but also relieves repression of asparaginase and thymine 7-hydroxylase syntheses by atmospheric oxygen while reducing expression of certain other structural genes (32,163,164). areA 300 is an "in frame" 417-bp tandem duplication that includes the whole DNA-binding region and extending 74 codons 3' to it (32).…”

Production of L-asparaginase from Natural Substrates by Aspergillus terreus MTCC 1782: Optimization of Carbon Source and Operating Conditions

“…(Foda et al, 1980), Rhodosporidium toruloides (Ramakrishnan and Joseph, 1996) were reported to produce L-asparaginase. L-Asparaginase from fungal sources such as Aspergillus nidulans (Shaffer et al, 1988) using different synthetic substrates and Aspergillus terreus isolated from decomposing vegetables were not toxic and appeared to have myelosuppressive and immunosuppressive activity (Ali et al, 1994). Mesophilic fungus Cylindrocarpon obtusisporum MB-10 (Rahae et al, 1990), Aspergillus tamari and Aspergillus terreus (Sarquis et al, 2004;, Aspergillus niger (Mishra., 2006) and Aspergillus sp.…”

Genetic Analysis of the TOR Pathway in Aspergillus nidulans

“…1). The heterozygous diploid torA3/torA ϩ showed increased sensitivity to 10 mM DL-aspartic acid ␤-hydroxamate in the presence of NH 4 ϩ , indicating partial derepression of the asparaginase gene ahrA (11,27). Both fprA Ϫ and jipA Ϫ showed weak pleiotropic effects on several nitrogen sources and had severely reduced growth on 2-pyrrolidone.…”