Control by pH of Cell Wall Peroxidase Activity Involved in Lignification

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Abstract
PH affected both conyferyl alcohol (CA) oxidation and NADH-dependent H2O2 formation catalysed by cell wall-bound peroxidase from lupin. The kinetics of CA oxidation shown at pH 5.0 was of the Michaelian-type, independently of the physical state (bound or soluble) of the enzyme in the cell wall, whereas at pH 8.0, it was cooperative. The affinity of the enzyme to H2O2and the rate of H2O2 formation were higher at pH 8.0 than at pH 5.0. The kinetics of H2O2 formation at pH 8.0 was strongly cooperative. These results are discussed with respect to the important role of pH in the regulation of cell wall peroxidase activities involved in lignification.