Functional analysis and transcriptional regulation of two orthologs of ARO10, encoding broad‐substrate‐specificity 2‐oxo‐acid decarboxylases, in the brewing yeast Saccharomyces pastorianus CBS1483

This study focuses on ARO10, a 2 oxo‐acid decarboxylase involved in production of higher alcohols. In S.pastorianus CBS1483, four ARO10 copies were identified, three resembled S.cerevisiae ARO10 and one S. eubayanus ARO10. Substrate specificities of lager strain (Lg)ScAro10 and LgSeubAro10 were compared by individually expressing them in a pdc1Δ‐pdc5Δ‐pdc6Δ‐aro10Δ‐thi3Δ S. cerevisiae strain. Both isoenzymes catalysed decarboxylation of the 2‐oxo‐acids derived from branched‐chain, sulphur‐containing amino‐acids isoleucine, and preferably phenylpyruvate. Expression of both alleles was induced by phenylalanine, however in contrast to the S.cerevisiae strain the two genes were not induced by leucine. Additionally LgSeubARO10 showed higher basal expression levels during growth with ammonia. ARO80, which encodes ARO10 transcriptional activator, is located on CHRIV and counts three Sc–like and one Seub‐like copies. Deletion of LgSeubARO80 did not affect LgSeubARO10 phenylalanine induction, revealing ‘trans’ regulation across the subgenomes. ARO10 transcript levels showed a poor correlation with decarboxylase activities. These results provide insights on flavour formation in S.pastorianus and illustrate the complexity of functional characterization in aneuploid strains.
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Source: FEMS Yeast Research - May 21, 2013 Category: Research Authors: Irina Bolat, Gabriele Romagnoli, Feibai Zhu, Jack T. Pronk, Jean‐Marc Daran Tags: Research Paper Source Type: research