AN EXAMINATION OF THE PEROXIDASES FROM LUPINUS-ALBUS L HYPOCOTYLS

Peroxidases (EC 1.11.1.7) from hypocotyls of Lupinus albus L. cv. Rio Maior have been characterised using one- and two-dimensional, native e lectrophoretic techniques. Data are presented showing the complexity i n charge and molecular size or shape of these peroxidases. We report t he finding of a new acidic peroxidase and several new basic peroxidase s in these hypocotyls, and of their stability to treatments considered to break ligand-induced variants and conformational variants derived from differences in polypeptide folding. Densitometric data demonstrat e that these new peroxidases contribute up to 60% of the total peroxid ase activity in hypocotyls. Studies of intercellular fluid, cell-wall and soluble fractions, with assays of purity were conducted in an atte mpt to define the subcellular locations of these additional peroxidase s. The acidic form (pI 4.1) is greatly enriched in soluble fractions, three of the basic peroxidases (pIs 9.5, 9.7 and >9.7) are strongly as sociated to the cell wall, ad a minor, basic component (pI 9.7) is enr iched in the intercellular fluid. Individual peroxidase activities wit h the substrates coniferyl alcohol, ferulic acid or indole acetic acid were compared by densitometric analysis of zymograms with those for g uaiacol, and notable differences between these peroxidases in their ca pacity to oxidise indole acetic acid in vitro were identified. The pos sible functions of these peroxidases in vivo and their implications to current understanding of peroxidases in L. albus are discussed.