Purification and properties of glycolate oxidase from plants with different photosynthetic pathways: Distinctness of C₄ enzyme from that of a C₃ species and a C₃-C₄ intermediate

Abstract

Glycolate oxidase (GO; EC 1.1.3.1) was purified from the leaves of three plant species:Amaranthus hypochondriacus L.(NAD-ME type C₄ dicot),Pisum sativum L. (C₃ species) andParthenium hysterophorus L. (C₃-C₄. intermediate). A flavin moiety was present in the enzyme from all the three species. The enzyme from the C₄ plant had a low specific activity, exhibited lower K_M for glycolate, and required a lower pH for maximal activity, compared to the C₃ enzyme. The enzyme from the C₄ species oxidized glyoxylate at <10% of the rate with glycolate, while the GO from the C₃ plant oxidized glyoxylate at a rate of about 35 to 40% of that with glycolate. The sensitivity of GO from C₄ plant to α-hydroxypyridinemethane sulfonate, 2-hydroxy-3-butynoate and other inhibitors was less than that of the enzyme from C₃ source. The properties of GO from Parthenium hysterophorus, were similar to those of the enzyme fromPisum sativum. The characteristics of glycolate oxidase from leaves of a C₄ plant, Amaranthus hypochondriacus are different from those of the C₃ species or the C₃-C₄ intermediate.