Modification of maize leaf phosphoenolpyruvate carboxylase with fluorescein isothiocyanate
1994
Wu, M.X. | Wedding, R.T.
Fluorescein isothiocyanate inactivates phosphoenolpyruvate carboxylase from maize leaves, presumably by reacting with lysyl groups. The reaction appears to involve at least two groups of lysines on the enzyme. The more rapid reaction is with groups which are protected by the substrate magnesium phosphoenolpyruvate and thus probably are located in the active site. In addition, fluorescein isothiocyanate apparently binds more slowly at a site which desensitizes the enzyme to activation by glucose-6-phosphate. Using the fluorescence of the complex of fluorescein isothiocyanate with phosphoenolpyruvate carboxylase it was shown that both magnesium phosphoenolpyruvate and glucose-6-phosphate cause changes in the conformation of the enzyme and influence the binding of fluorescein isothiocyanate as well. Light scattering measurements showed that fluorescein isothiocyanate induced disaggregation of the enzyme, while glucose-6-phosphate caused aggregation, although less when fluorescein isothiocyanate was present.
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