Phosphoglycerate Kinase: Difference between revisions

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== Kinetics ==

Given that Phosphoglycerate kinase is a monomeric protein standard Michealis-Menton kinetics would be expected; however, this is not the case. Multiple experiments have shown that the data, when transformed into either double-reciprocal or Eadie-Hofstee plots is non-linear; Eadie-Hofstee plots curve upward. One possible explanation for the non-linearity, negative cooperativity, is ruled out because PGK does not have multiple subunits. In one study that conducted kinetic tests with a 1000 fold range of substrates, at the highest concentrations of substrate the rate was still increasing; this puts the Km value in the 2-5mM range <ref> Scopes, Robert. 1977. The Steady State Kinetics of Yeast Phosphoglycerate Kinase. European Journal of Biochemistry. 85, 503-516 </ref>

Given that Phosphoglycerate kinase is a monomeric protein standard Michealis-Menton kinetics would be expected; however, this is not the case. Multiple experiments have shown that the data, when transformed into either double-reciprocal or Eadie-Hofstee plots is non-linear; Eadie-Hofstee plots curve upward. One possible explanation for the non-linearity, negative cooperativity, is ruled out because PGK does not have multiple subunits. In one study that conducted kinetic tests with a 1000 fold range of substrates, at the highest concentrations of substrate the rate was still increasing; this puts the Km value in the 2-5mM range <ref> Scopes, Robert. 1977. The Steady State Kinetics of Yeast Phosphoglycerate Kinase. European Journal of Biochemistry. 85, 503-516 </ref> Recently, a new model was proposed to explain this conflict between the seemingly negative cooperative kinetics and the monomeric structure of PGK. The enzyme may form a complex with the metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase. This multi-subunit complex would be capable of the negative cooperativity that is indicated by the non-linear kinetics of PGK.<ref> Macioszek, Jerzy et al. 1990. Kinetics of the Two-Enzyme Phosphoglycerate Kinase/Glyceraldehyde-3-Phosphate Dehydrogenase Couple. Plant Physiology 94: 291-296.</ref>.

Phosphoglycerate Kinase: Difference between revisions

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Revision as of 06:21, 9 May 2011 view source Brandon Tritle (talk \| contribs) 6 edits No edit summary ← Older edit		Revision as of 06:26, 9 May 2011 view source Brandon Tritle (talk \| contribs) 6 edits No edit summary Newer edit →
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	== Kinetics ==		== Kinetics ==

	Given that Phosphoglycerate kinase is a monomeric protein standard Michealis-Menton kinetics would be expected; however, this is not the case. Multiple experiments have shown that the data, when transformed into either double-reciprocal or Eadie-Hofstee plots is non-linear; Eadie-Hofstee plots curve upward. One possible explanation for the non-linearity, negative cooperativity, is ruled out because PGK does not have multiple subunits. In one study that conducted kinetic tests with a 1000 fold range of substrates, at the highest concentrations of substrate the rate was still increasing; this puts the Km value in the 2-5mM range <ref> Scopes, Robert. 1977. The Steady State Kinetics of Yeast Phosphoglycerate Kinase. European Journal of Biochemistry. 85, 503-516 </ref>		Given that Phosphoglycerate kinase is a monomeric protein standard Michealis-Menton kinetics would be expected; however, this is not the case. Multiple experiments have shown that the data, when transformed into either double-reciprocal or Eadie-Hofstee plots is non-linear; Eadie-Hofstee plots curve upward. One possible explanation for the non-linearity, negative cooperativity, is ruled out because PGK does not have multiple subunits. In one study that conducted kinetic tests with a 1000 fold range of substrates, at the highest concentrations of substrate the rate was still increasing; this puts the Km value in the 2-5mM range <ref> Scopes, Robert. 1977. The Steady State Kinetics of Yeast Phosphoglycerate Kinase. European Journal of Biochemistry. 85, 503-516 </ref> Recently, a new model was proposed to explain this conflict between the seemingly negative cooperative kinetics and the monomeric structure of PGK. The enzyme may form a complex with the metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase. This multi-subunit complex would be capable of the negative cooperativity that is indicated by the non-linear kinetics of PGK.<ref> Macioszek, Jerzy et al. 1990. Kinetics of the Two-Enzyme Phosphoglycerate Kinase/Glyceraldehyde-3-Phosphate Dehydrogenase Couple. Plant Physiology 94: 291-296.</ref>.