title: L-galactonate dehydratase is part of the fungal path for D-galacturonic acid catabolism.
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.
authors.affiliation: VTT Biotechnology, Espoo, Finland.
authors.forename: Satu
authors.initials: S
authors.lastname: Kuorelahti
authors.forename: Paula
authors.initials: P
authors.lastname: Jouhten
authors.forename: Hannu
authors.initials: H
authors.lastname: Maaheimo
authors.forename: Merja
authors.initials: M
authors.lastname: Penttilä
authors.forename: Peter
authors.initials: P
authors.lastname: Richard
mesh_terms: D015152:Blotting, Northern; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005985:Glyceraldehyde; D005990:Glycerol / Q000378:metabolism; D006603:Hexuronic Acids / Q000378:metabolism*; D006836:Hydro-Lyases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D035901:Hypocrea / Q000201:enzymology / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D006603:Hexuronic Acids; D005985:Glyceraldehyde; C007819:galacturonic acid; D019289:Pyruvic Acid; D006836:Hydro-Lyases; C019607:galactonate dehydratase; D005990:Glycerol