VIEW ARTICLE

Physiology and Biochemistry

Localization of Enzymes of Oxalate Biosynthesis in Microbodies of Sclerotium rolfsii. V. N. Armentrout, Former research associate, Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, Present address of senior author: Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768; L. B. Graves, Jr.(2), and D. P. Maxwell(3). (2)(3)Research specialist, and professor, respectively, Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706. Phytopathology 68:1597-1599. Accepted for publication 26 July 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1597.

Sclerotium rolfsii secretes oxalic acid when grown on a medium containing 1% sodium polypectate. Mitochondria and microbodies were partially purified from hyphae grown under these conditions by centrifugation of mycelial homogenates on a sucrose density gradient in a zonal rotor. Peak activity of malate dehydrogenase, a mitochondrial marker, occurred at a buoyant density of 1.162 g/cm³, whereas the peak activity of catalase, a microbody marker, occurred at 1.196 g/cm³. The two key enzymes of oxalic acid biosynthesis, glyoxylate dehydrogenase and isocitrate lyase, had distributions similar to that of catalase, and hence appear to be localized in microbodies. No malate synthase activity was detectable. This is the first report of the involvement of microbodies in a process essential to the pathogenic capabilities of a fungus.