Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel
The properties of liver pyruvate kinase (PyK) from summer-active Arctic ground squirrel (Citellus undulatus) were examined over the physiological temperature range of the animal. One form of the enzyme with a pI (isoelectric point) value of 5.3 was observed and exhibited kinetics similar to those of...
Published in: | Canadian Journal of Biochemistry |
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Canadian Science Publishing
1974
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crcansciencepubl:10.1139/o74-079 2023-12-17T10:23:53+01:00 Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel Behrisch, Hans W. Johnson, Craig E. 1974 http://dx.doi.org/10.1139/o74-079 http://www.nrcresearchpress.com/doi/pdf/10.1139/o74-079 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Biochemistry volume 52, issue 6, page 547-559 ISSN 0008-4018 General Medicine journal-article 1974 crcansciencepubl https://doi.org/10.1139/o74-079 2023-11-19T13:39:04Z The properties of liver pyruvate kinase (PyK) from summer-active Arctic ground squirrel (Citellus undulatus) were examined over the physiological temperature range of the animal. One form of the enzyme with a pI (isoelectric point) value of 5.3 was observed and exhibited kinetics similar to those of L-type PyK. This form has a molecular weight of 243 000, similar to that of M-type PyK. Enzyme–phosphoenolpyruvate (PEP) affinity falls with decreasing temperature while affinity for ADP increases under these conditions. The effect of temperature upon extent of negative cooperativity of PEP binding and its possible physiological importance are briefly discussed. Fructose-1,6-phosphate (FDP) increases the affinity of PyK for PEP but has no effect upon enzyme-ADP interaction. However, V max in the presence of saturating concentrations of both substrates is increased two to threefold by FDP, the allosteric activator. Ground squirrel PyK is inhibited by ATP. Inhibition by ATP of PyK activity is diminished by decreasing the temperature or by increasing the concentrations of substrate. FDP reverses this inhibition but the degree of reversal is sensitive to substrate concentration and temperature. Inhibition by ATP is competitive for the PEP site and appears to be of the "mixed-competitive" variety when carried out at varying concentrations of ADP. Inhibition by alanine is noncompetitive for both substrate sites. As a result of the very high concentrations of amino acids needed to obtain appreciable inhibition of live PyK, this does not appear to be a physiological means of regulation of enzyme activity. The effect of intermediates of the glycolytic, pentose shunt, and Krebs acid cycle pathways upon PyK activity is briefly discussed. Inosine nucleotides, involved in the reversal of the PyK reaction by phosphoenolpyruvate carboxykinase, have a strong modulating effect upon PyK activity. These data suggest formal mechanisms for the regulation of liver PyK in the ground squirrel. Article in Journal/Newspaper Arctic ground squirrel Arctic Canadian Science Publishing (via Crossref) Arctic Krebs ENVELOPE(-61.467,-61.467,-64.633,-64.633) Canadian Journal of Biochemistry 52 6 547 559 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Medicine |
spellingShingle |
General Medicine Behrisch, Hans W. Johnson, Craig E. Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel |
topic_facet |
General Medicine |
description |
The properties of liver pyruvate kinase (PyK) from summer-active Arctic ground squirrel (Citellus undulatus) were examined over the physiological temperature range of the animal. One form of the enzyme with a pI (isoelectric point) value of 5.3 was observed and exhibited kinetics similar to those of L-type PyK. This form has a molecular weight of 243 000, similar to that of M-type PyK. Enzyme–phosphoenolpyruvate (PEP) affinity falls with decreasing temperature while affinity for ADP increases under these conditions. The effect of temperature upon extent of negative cooperativity of PEP binding and its possible physiological importance are briefly discussed. Fructose-1,6-phosphate (FDP) increases the affinity of PyK for PEP but has no effect upon enzyme-ADP interaction. However, V max in the presence of saturating concentrations of both substrates is increased two to threefold by FDP, the allosteric activator. Ground squirrel PyK is inhibited by ATP. Inhibition by ATP of PyK activity is diminished by decreasing the temperature or by increasing the concentrations of substrate. FDP reverses this inhibition but the degree of reversal is sensitive to substrate concentration and temperature. Inhibition by ATP is competitive for the PEP site and appears to be of the "mixed-competitive" variety when carried out at varying concentrations of ADP. Inhibition by alanine is noncompetitive for both substrate sites. As a result of the very high concentrations of amino acids needed to obtain appreciable inhibition of live PyK, this does not appear to be a physiological means of regulation of enzyme activity. The effect of intermediates of the glycolytic, pentose shunt, and Krebs acid cycle pathways upon PyK activity is briefly discussed. Inosine nucleotides, involved in the reversal of the PyK reaction by phosphoenolpyruvate carboxykinase, have a strong modulating effect upon PyK activity. These data suggest formal mechanisms for the regulation of liver PyK in the ground squirrel. |
format |
Article in Journal/Newspaper |
author |
Behrisch, Hans W. Johnson, Craig E. |
author_facet |
Behrisch, Hans W. Johnson, Craig E. |
author_sort |
Behrisch, Hans W. |
title |
Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel |
title_short |
Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel |
title_full |
Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel |
title_fullStr |
Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel |
title_full_unstemmed |
Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel |
title_sort |
regulatory properties of pyruvate kinase from liver of the summer-active arctic ground squirrel |
publisher |
Canadian Science Publishing |
publishDate |
1974 |
url |
http://dx.doi.org/10.1139/o74-079 http://www.nrcresearchpress.com/doi/pdf/10.1139/o74-079 |
long_lat |
ENVELOPE(-61.467,-61.467,-64.633,-64.633) |
geographic |
Arctic Krebs |
geographic_facet |
Arctic Krebs |
genre |
Arctic ground squirrel Arctic |
genre_facet |
Arctic ground squirrel Arctic |
op_source |
Canadian Journal of Biochemistry volume 52, issue 6, page 547-559 ISSN 0008-4018 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/o74-079 |
container_title |
Canadian Journal of Biochemistry |
container_volume |
52 |
container_issue |
6 |
container_start_page |
547 |
op_container_end_page |
559 |
_version_ |
1785560968891203584 |