Biochemical and spectroscopic characterization of catechol oxidase from sweet potatoes (<i>Ipomoea batatas</i>) containing a type‐3 dicopper center¹

Abstract

Two catechol oxidases have been isolated from sweet potatoes ( Ipomoea batatas ) and purified to homogeneity. The two isozymes have been characterized by EXAFS, EPR‐, UV/Vis‐spectroscopy, isoelectric focusing, and MALDI‐MS and have been shown to contain a dinuclear copper center. Both are monomers with a molecular mass of 39 kDa and 40 kDa, respectively. Substrate specificity and NH 2 ‐terminal sequences have been determined. EXAFS data for the 39 kDa enzyme reveal a coordination number of four for each Cu in the resting form and suggest a Cu(II)‐Cu(II) distance of 2.9 Å for the native met form and 3.8 Å for the oxy form.