LaeA, a regulator of secondary metabolism in fungi, controls expression of two genes encoding NRPS8208;like enzymes in Aspergillus flavus, termed LnaA and LnbA. Although these enzymes resembleÂ α 8208;aminoadipate reductases (i.e., primary metabolism enzymes), gene deletion and knockdown experiments pointed to a role for LnaA and LnbA in secondary metabolism. Specifically, the biosyntheses of heterocyclic L8208;tyrosine8208;derived natural products are dependent on these enzymes. Genetic data is also suggestive of functional redundancy of these two enzymes. Hexahistidine8208;tagged LnaA and LnbA were heterologously produced, and assayed using the amino acid8208;dependent ATP8208;pyrophosphate exchange method. L8208;tyrosine was identified as clearly preferred substrate of both enzymes. Further biochemical characterization established divergent temperature and pH8208;optima, and differences regarding stereospecificity. Our biochemical experiments prove that the LnaA and LnbA substrate spectrum is compatible with their tentative heterocyclic products. Further, participation ofÂ α 8208;aminoadipate reductase8208;like NRPSs in secondary metabolism and functional redundancy of LnaA and LnbA, anticipated by genetic methods, is supported by the substrate spectrum of these enzymes.
Full conference title:
11 th European Conference on Fungal Genetics
- ECFG 11th (2012)