PURIFICATION AND PROPERTIES OF GLYCOLATE OXIDASE FROM PLANTS WITH DIFFERENT PHOTOSYNTHETIC PATHWAYS - DISTINCTNESS OF C-4 ENZYME FROM THAT OF A C-3 SPECIES AND A C-3-C-4 INTERMEDIATE

Glycolate oxidase (GO; EC 1.1.3.1) was purified from the leaves of thr ee plant species: Amaranthus hypochondriacus L.(NAD-ME type C-4 dicot) , Pisum sativum L. (C-3 species) and Parthenium hysterophorus L. (C-3- C-4. intermediate). A flavin moiety was present in the enzyme from all the three species. The enzyme from the C-4 plant had a low specific a ctivity, exhibited lower K-M for glycolate, and required a lower pH fo r maximal activity, compared to the C-3 enzyme. The enzyme from the C- 4 species oxidized glyoxylate at < 10% of the rate with glycolate, whi le the GO from the C-3 plant oxidized glyoxylate at a rate of about 35 to 40% of that with glycolate. The sensitivity of GO from C-4 plant t o alpha-hydroxypyridinemethane sulfonate, 2-hydroxy-3-butynoate and ot her inhibitors was less than that of the enzyme from C-3 source. The p roperties of GO from Parthenium hysterophorus, were similar to those o f the enzyme from Pisum sativum. The characteristics of glycolate oxid ase from leaves of a C-4 plant, Amaranthus hypochondriacus are differe nt from those of the C-3 species or the C-3-C-4 intermediate.