Laccases in higher plants
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The optimum method of screening for laccase in higher plant leaves was ascertained, and the method used to screen a number of plants. Four fruits from trees of the genus Prunus were also screened for laccase. A novel laccase substrate, 4-hydroxyindole, was used as the assay substrate alongside other traditional laccase substrates. Laccase was identified in most of the species studied. 4-Hydroxyindole appears to be a universal laccase substrate. However, most of the higher plant laccases identified did not oxidise syringaldazine, a common substrate for fungal laccases. Yield of laccase was found to be significantly increased by treatment with cell wall degrading enzymes, particularly Ultrazyme-100 for leaves, and Rapidase® Press for fruit. This observation may have important implications in the study of lignification. The identities of all the enzymes isolated were verified as laccases by inhibitor tests. CTAB was found to inhibit all the laccases studied. Also, a novel laccase inhibitor, N-hydroxyglycine, was studied, and found to only inhibit a small proportion of the laccases studied. The type of inhibition in fruit laccases was identified as non competitive.