Plant Physiol.
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Plant Physiology 98:774-776 (1992)
© 1992 American Society of Plant Biologists

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Metabolism and Enzymology

Hysteresis and Cooperative Behavior of a Latent Plant Polyphenoloxidase 1

Edelmira Valero and Francisco García-Carmona

Departamento de Química-Física, E. U. Politécnica de Albacete, Universidad de Castilla-La Mancha, E-02006 Albacete, Spain, Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Murcia, E-30001-Murcia, Spain

Appearance of a lag period dependent on pH in the expression of the catecholase activity of a polyphenoloxidase extracted in a latent state from Airen grape (Vitis vinifera L.) berries, is revealed, suggesting the hysteretic nature of the enzyme. The lag time was independent of enzyme concentration, indicating that slow pH-induced conformational changes in the protein must occur during assay. Results obtained by varying substrate concentration show that the system presents hyperbolic or cooperative kinetics depending on the pH of the assay.

1 This work was partially supported by a grant from the Comisión Interministerial de Ciencia y Tecnología (Spain), Proyecto No. AGR-89-0296.






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Copyright © 1992 by the American Society of Plant Biologists