Identification of the galactitol dehydrogenase, LadB, that is part of the oxido-reductive d-galactose catabolic pathway in Aspergillus niger

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Abstract

For the catabolism of d-galactose three different metabolic pathways have been described in filamentous fungi. Apart from the Leloir pathway and the oxidative pathway, there is an alternative oxido-reductive pathway. This oxido-reductive pathway has similarities to the metabolic pathway of l-arabinose, and in Trichoderma reesei (Hypocrea jecorina) and Aspergillus nidulans the same enzyme is employed for the oxidation of l-arabitol and galactitol. Here we show evidence that in Aspergillus niger l-arabitol dehydrogenase (LadA) is not involved in the d-galactose metabolism; instead another dehydrogenase encoding gene, ladB, is induced in response to d-galactose and galactitol and functions as a galactitol dehydrogenase. Deletion of ladB in A. niger results in growth arrest on galactitol and significantly slower growth on d-galactose supplemented with a small amount of d-xylose. d-galactose alone cannot be utilised by A. niger and the addition of d-xylose stimulates growth on d-galactose via transcriptional activation of the d-xylose-inducible reductase gene, xyrA. XyrA catalyses the first step of the d-galactose oxido-reductive pathway, the reduction to galactitol, which in turn seems to be an inducer of the downstream genes such as LadB. The deletion of xyrA results in reduced growth on d-galactose. The ladB gene was expressed in the heterologous host Saccharomyces cerevisiae and the tagged and purified enzyme characterised. LadB and LadA have similar in vitro activity with galactitol. It was confirmed that the reaction product of the LadB reaction from galactitol is l-xylo-3-hexulose as in the case of the T. reesei Lad1.

Original languageEnglish
Pages (from-to)152-159
JournalFungal Genetics and Biology
Volume49
Issue number2
DOIs
Publication statusPublished - 1 Feb 2012
MoE publication typeA1 Journal article-refereed

Fingerprint

Aspergillus niger
Galactitol
Galactose
Oxidoreductases
Xylose
Growth
Metabolic Networks and Pathways
Genes
Hypocrea
Aspergillus nidulans
Aldehyde Reductase
Arabinose
Trichoderma
galactitol 2-dehydrogenase
Enzymes
Transcriptional Activation
Saccharomyces cerevisiae
Fungi

Keywords

  • Aspergillus niger
  • D-Galactose
  • D-Galactose metabolism
  • Galactitol
  • Galactitol dehydrogenase
  • L-Arabitol dehydrogenase
  • L-Xylo-3-hexulose

Cite this

@article{4d9429b4b8a34fc4949216e7ab61f40b,
title = "Identification of the galactitol dehydrogenase, LadB, that is part of the oxido-reductive d-galactose catabolic pathway in Aspergillus niger",
abstract = "For the catabolism of d-galactose three different metabolic pathways have been described in filamentous fungi. Apart from the Leloir pathway and the oxidative pathway, there is an alternative oxido-reductive pathway. This oxido-reductive pathway has similarities to the metabolic pathway of l-arabinose, and in Trichoderma reesei (Hypocrea jecorina) and Aspergillus nidulans the same enzyme is employed for the oxidation of l-arabitol and galactitol. Here we show evidence that in Aspergillus niger l-arabitol dehydrogenase (LadA) is not involved in the d-galactose metabolism; instead another dehydrogenase encoding gene, ladB, is induced in response to d-galactose and galactitol and functions as a galactitol dehydrogenase. Deletion of ladB in A. niger results in growth arrest on galactitol and significantly slower growth on d-galactose supplemented with a small amount of d-xylose. d-galactose alone cannot be utilised by A. niger and the addition of d-xylose stimulates growth on d-galactose via transcriptional activation of the d-xylose-inducible reductase gene, xyrA. XyrA catalyses the first step of the d-galactose oxido-reductive pathway, the reduction to galactitol, which in turn seems to be an inducer of the downstream genes such as LadB. The deletion of xyrA results in reduced growth on d-galactose. The ladB gene was expressed in the heterologous host Saccharomyces cerevisiae and the tagged and purified enzyme characterised. LadB and LadA have similar in vitro activity with galactitol. It was confirmed that the reaction product of the LadB reaction from galactitol is l-xylo-3-hexulose as in the case of the T. reesei Lad1.",
keywords = "Aspergillus niger, D-Galactose, D-Galactose metabolism, Galactitol, Galactitol dehydrogenase, L-Arabitol dehydrogenase, L-Xylo-3-hexulose",
author = "Dominik Mojzita and Koivistoinen, {Outi M.} and Hannu Maaheimo and Merja Penttil{\"a} and Laura Ruohonen and Peter Richard",
note = "CA2: TK402 CA2: TK400 SDA: BIC ISI: GENETICS & HEREDITY",
year = "2012",
month = "2",
day = "1",
doi = "10.1016/j.fgb.2011.11.005",
language = "English",
volume = "49",
pages = "152--159",
journal = "Fungal Genetics and Biology",
issn = "1087-1845",
publisher = "Academic Press",
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TY - JOUR

T1 - Identification of the galactitol dehydrogenase, LadB, that is part of the oxido-reductive d-galactose catabolic pathway in Aspergillus niger

AU - Mojzita, Dominik

AU - Koivistoinen, Outi M.

AU - Maaheimo, Hannu

AU - Penttilä, Merja

AU - Ruohonen, Laura

AU - Richard, Peter

N1 - CA2: TK402 CA2: TK400 SDA: BIC ISI: GENETICS & HEREDITY

PY - 2012/2/1

Y1 - 2012/2/1

N2 - For the catabolism of d-galactose three different metabolic pathways have been described in filamentous fungi. Apart from the Leloir pathway and the oxidative pathway, there is an alternative oxido-reductive pathway. This oxido-reductive pathway has similarities to the metabolic pathway of l-arabinose, and in Trichoderma reesei (Hypocrea jecorina) and Aspergillus nidulans the same enzyme is employed for the oxidation of l-arabitol and galactitol. Here we show evidence that in Aspergillus niger l-arabitol dehydrogenase (LadA) is not involved in the d-galactose metabolism; instead another dehydrogenase encoding gene, ladB, is induced in response to d-galactose and galactitol and functions as a galactitol dehydrogenase. Deletion of ladB in A. niger results in growth arrest on galactitol and significantly slower growth on d-galactose supplemented with a small amount of d-xylose. d-galactose alone cannot be utilised by A. niger and the addition of d-xylose stimulates growth on d-galactose via transcriptional activation of the d-xylose-inducible reductase gene, xyrA. XyrA catalyses the first step of the d-galactose oxido-reductive pathway, the reduction to galactitol, which in turn seems to be an inducer of the downstream genes such as LadB. The deletion of xyrA results in reduced growth on d-galactose. The ladB gene was expressed in the heterologous host Saccharomyces cerevisiae and the tagged and purified enzyme characterised. LadB and LadA have similar in vitro activity with galactitol. It was confirmed that the reaction product of the LadB reaction from galactitol is l-xylo-3-hexulose as in the case of the T. reesei Lad1.

AB - For the catabolism of d-galactose three different metabolic pathways have been described in filamentous fungi. Apart from the Leloir pathway and the oxidative pathway, there is an alternative oxido-reductive pathway. This oxido-reductive pathway has similarities to the metabolic pathway of l-arabinose, and in Trichoderma reesei (Hypocrea jecorina) and Aspergillus nidulans the same enzyme is employed for the oxidation of l-arabitol and galactitol. Here we show evidence that in Aspergillus niger l-arabitol dehydrogenase (LadA) is not involved in the d-galactose metabolism; instead another dehydrogenase encoding gene, ladB, is induced in response to d-galactose and galactitol and functions as a galactitol dehydrogenase. Deletion of ladB in A. niger results in growth arrest on galactitol and significantly slower growth on d-galactose supplemented with a small amount of d-xylose. d-galactose alone cannot be utilised by A. niger and the addition of d-xylose stimulates growth on d-galactose via transcriptional activation of the d-xylose-inducible reductase gene, xyrA. XyrA catalyses the first step of the d-galactose oxido-reductive pathway, the reduction to galactitol, which in turn seems to be an inducer of the downstream genes such as LadB. The deletion of xyrA results in reduced growth on d-galactose. The ladB gene was expressed in the heterologous host Saccharomyces cerevisiae and the tagged and purified enzyme characterised. LadB and LadA have similar in vitro activity with galactitol. It was confirmed that the reaction product of the LadB reaction from galactitol is l-xylo-3-hexulose as in the case of the T. reesei Lad1.

KW - Aspergillus niger

KW - D-Galactose

KW - D-Galactose metabolism

KW - Galactitol

KW - Galactitol dehydrogenase

KW - L-Arabitol dehydrogenase

KW - L-Xylo-3-hexulose

UR - http://www.scopus.com/inward/record.url?scp=84856793741&partnerID=8YFLogxK

U2 - 10.1016/j.fgb.2011.11.005

DO - 10.1016/j.fgb.2011.11.005

M3 - Article

VL - 49

SP - 152

EP - 159

JO - Fungal Genetics and Biology

JF - Fungal Genetics and Biology

SN - 1087-1845

IS - 2

ER -