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Metabolism of [C-14] glutamate and [C-14] glutamine by the ectomycorrhizal fungus Paxillus involutus

Chalot, Mickel; Brun, Annick; Finlay, Roger D. and Söderström, Bengt LU (1994) In Microbiology 140. p.1641-1649
Abstract
To examine pathways of glutamate and glutamine metabolism in the ectomycorrhizal fungus Paxillus involutus, tracer kinetic experiments were performed using L-[U-C-14]glutamate and L-[U-C-14]glutamine and the enzyme inhibitors methionine sulfoximine (MSX), azaserine (AZA) and aminooxyacetate (AOA). When [C-14]glutamate was supplied to fungal cultures, 25% of the radioactivity of the amino acid fraction was incorporated into glutamine after 5 min feeding, but MSX inhibited incorporation of C-14 into glutamine by 85%, suggesting the rapid operation of glutamine synthetase. Conversely, when P. involutus was fed with [C-14]glutamine, 46% of the label was found in glutamate within 30 min of feeding and AZA inhibited glutamate formation by 90%.... (More)
To examine pathways of glutamate and glutamine metabolism in the ectomycorrhizal fungus Paxillus involutus, tracer kinetic experiments were performed using L-[U-C-14]glutamate and L-[U-C-14]glutamine and the enzyme inhibitors methionine sulfoximine (MSX), azaserine (AZA) and aminooxyacetate (AOA). When [C-14]glutamate was supplied to fungal cultures, 25% of the radioactivity of the amino acid fraction was incorporated into glutamine after 5 min feeding, but MSX inhibited incorporation of C-14 into glutamine by 85%, suggesting the rapid operation of glutamine synthetase. Conversely, when P. involutus was fed with [C-14]glutamine, 46% of the label was found in glutamate within 30 min of feeding and AZA inhibited glutamate formation by 90%. Taken together, these data indicate that glutamate synthase (GOGAT) is the major enzyme of glutamine degradation. In addition, the strong inhibition of glutamine utilization by AOA indicates that glutamine catabolism in P. involutus might involve a transamination process as an alternative pathway to GOCAT for glutamine degradation. The high (CO2)-C-14 evolution shows that glutamate and glutamine are further actively consumed as respiratory substrates, being channelled through the tricarboxylic acid (TCA) cycle and oxidized as CO2. It appears that synthesis of amino acid precursors during TCA cycle operation is an essential step far aspartate and alanine synthesis through aminotransferase activities in P. involutus. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ectomycorrhizal fungi, glutamine metabolism, glutamate metabolism, Paxillus involutus
in
Microbiology
volume
140
pages
1641 - 1649
publisher
MAIK Nauka/Interperiodica
ISSN
1465-2080
DOI
10.1099/13500872-140-7-1641
language
English
LU publication?
yes
id
47f1b654-ebcc-4e3d-b563-aa20cba6f744 (old id 2226326)
date added to LUP
2012-01-11 16:11:36
date last changed
2016-04-15 19:16:21
@article{47f1b654-ebcc-4e3d-b563-aa20cba6f744,
  abstract     = {To examine pathways of glutamate and glutamine metabolism in the ectomycorrhizal fungus Paxillus involutus, tracer kinetic experiments were performed using L-[U-C-14]glutamate and L-[U-C-14]glutamine and the enzyme inhibitors methionine sulfoximine (MSX), azaserine (AZA) and aminooxyacetate (AOA). When [C-14]glutamate was supplied to fungal cultures, 25% of the radioactivity of the amino acid fraction was incorporated into glutamine after 5 min feeding, but MSX inhibited incorporation of C-14 into glutamine by 85%, suggesting the rapid operation of glutamine synthetase. Conversely, when P. involutus was fed with [C-14]glutamine, 46% of the label was found in glutamate within 30 min of feeding and AZA inhibited glutamate formation by 90%. Taken together, these data indicate that glutamate synthase (GOGAT) is the major enzyme of glutamine degradation. In addition, the strong inhibition of glutamine utilization by AOA indicates that glutamine catabolism in P. involutus might involve a transamination process as an alternative pathway to GOCAT for glutamine degradation. The high (CO2)-C-14 evolution shows that glutamate and glutamine are further actively consumed as respiratory substrates, being channelled through the tricarboxylic acid (TCA) cycle and oxidized as CO2. It appears that synthesis of amino acid precursors during TCA cycle operation is an essential step far aspartate and alanine synthesis through aminotransferase activities in P. involutus.},
  author       = {Chalot, Mickel and Brun, Annick and Finlay, Roger D. and Söderström, Bengt},
  issn         = {1465-2080},
  keyword      = {ectomycorrhizal fungi,glutamine metabolism,glutamate metabolism,Paxillus involutus},
  language     = {eng},
  pages        = {1641--1649},
  publisher    = {MAIK Nauka/Interperiodica},
  series       = {Microbiology},
  title        = {Metabolism of [C-14] glutamate and [C-14] glutamine by the ectomycorrhizal fungus Paxillus involutus},
  url          = {http://dx.doi.org/10.1099/13500872-140-7-1641},
  volume       = {140},
  year         = {1994},
}