PMID: 2958457Oct 15, 1987

Correlation between hysteresis and allosteric properties for phosphofructokinase from Ascaris suum

The Journal of Biological Chemistry
P F CookB G Harris

Abstract

The Ascaris suum phosphofructokinase exhibits hysteretic transitions in the time course for fructose 6-phosphate (F6P) phosphorylation in addition to allosteric properties when assayed at pH values below 8. Conditions that enhance hysteretic changes also enhance cooperative interactions and thus there appears to be a link between hysteresis and cooperativity. Initiation of reaction with either F6P or phosphofructokinase results in a pronounced lag, while initiation of the reaction with MgATP results in a burst at pH values below 8. Under conditions in which a lag is evident, increasing the concentration of F6P in the assay decreases the lag, while under conditions where a burst is evident, increasing the concentration of MgATP in the assay decreases the burst. The lag is enzyme-dependent going to a limiting value at high enzyme concentration, while the burst is enzyme-independent. As the pH increases, the Hill coefficient for F6P decreases from a pH-independent value of 3 at low pH to a value of 1 above pH 8. Over the same pH range, the burst rate increases to a point that it is too fast to measure at pH 8 (that is, the time course is linear). Finally, at pH 6.9, the saturation curve for F6P becomes more cooperative with the Hi...Continue Reading

Related Concepts

Ascaris suum
PFKM
Fructose
Adenosine Triphosphate, Magnesium Salt
Protein Phosphorylation
Transcription Initiation
Phosphate Measurement
Phosphofructokinase
Ascaris
Binding (Molecular Function)

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