L-galactonate dehydratase is part of the fungal path for D-galacturonic acid catabolism

Satu Kuorelahti, Paula Jouhten, Hannu Maaheimo, Merja Penttilä, Peter Richard (Corresponding Author)

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Abstract

An L-galactonate dehydratase and the corresponding gene were identified from the mould Hypocrea jecorina (Trichoderma reesei). This novel enzyme converts L-galactonate to L-threo-3-deoxy-hexulosonate (2-keto-3-deoxy-L- galactonate). The enzyme is part of the fungal pathway for D-galacturonic acid catabolism, a pathway which is only partly known. It is the second enzyme of this pathway after the D-galacturonic acid reductase. L-galactonate dehydratase activity is present in H. jecorina cells grown on D-galacturonic acid but absent when other carbon sources are used for growth. A deletion of the L-galactonate dehydratase gene in H. jecorina results in a strain with no growth on D-galacturonic acid. The active enzyme was produced in the heterologous host Saccharomyces cerevisiae and characterized. It exhibited activity with L-galactonate and D-arabonate where the hydroxyl group of the C2 is in L- and the hydroxyl group of the C3 is in D-configuration in the Fischer projection. However, it did not exhibit activity with D-galactonate, D-gluconate, L-gulonate or D-xylonate where the hydroxyl groups of the C2 and C3 are in different configuration.

Original languageEnglish
Pages (from-to)1060-1068
Number of pages9
JournalMolecular Microbiology
Volume61
Issue number4
DOIs
Publication statusPublished - 1 Aug 2006
MoE publication typeA1 Journal article-refereed

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Keywords

  • dehydratase
  • l-galactonate
  • Trichoderma reesei
  • fungal
  • fungal path
  • catabolism
  • metabolomics
  • gene expression

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