May 1, 1976

Modification of the regulatory properties of pyruvate kinase of Neurospora by growth at elevated temperatures

Canadian Journal of Biochemistry
M KapoorA Braun


Pyruvate kinase (EC was isolated from Neurospora crassa mycelium grown at 28 degrees C (PK-28) and at 42 degrees C (PK-42). The regulatory properties, particularly the response towards the allosteric effector fructose 1,6-diphosphate (FDP), was different in the two enzymes. PK-28 showed an activation by FDP but PK-42, under comparable conditions, appeared to be activated by low concentrations of FDP and inhibited by higher ones. For PK-28, complex formation with FDP results in a lowering of the isoelectric point from 6.40 to 5.50, representing the pI of the unliganded enzyme and that of the complex, respectively. In contrast to this, PK-42 exhibits a weak binding to FDP as suggested by a lack of decrease in the isoelectric point on treatment with comparable concentrations of FDP. Studies with quenching of aromatic residue fluorescence of PK-28 and PK-42, following binding of FDP, indicate that although this ligand binds to both types of enzymes the affinity for the two is vastly different. Dissociation constants of 9.3 muM and 0.1 mM were calculated for the binding of FDP to PK-28 and PK-42, respectively. It is concluded that growth at elevated temperatures induced a conformational change in the pyruvate kinase leadin...Continue Reading

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Mentioned in this Paper

Neurospora crassa
Allosteric Site
Enzymes, antithrombotic
Pyruvate Kinase
Fluorescence Spectroscopy
Plasma Protein Binding Capacity
Protein Conformation
Enzymes for Treatment of Wounds and Ulcers

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