title: A protective association between catalase and isocitrate lyase in peroxisomes.
abstract: Glyoxysomes are specialized peroxisomes in germinating seeds, which catalyze many reactions that convert fatty acids into carbohydrates thus generating H(2)O(2). They are characterized by the presence of catalase (CAT, E.C. 1.11.1.6) in their matrix which protects cells from oxidative stress. Here, we investigated the possibility that a protein can be protected from oxidative damage by its association with CAT. We purified peroxisomal CAT from germinating castor beans by ion exchange, gel filtration, and hydroxylapatite chromatography. Gel filtration of the matrix proteins, cross-linking, and co-immunoprecipitation studies indicate that CAT associates with a glyoxysomal matrix protein, isocitrate lyase (ICL, E.C. 4.1.3.1). In addition, we found that H(2)O(2) inactivates ICL and degrades its product, glyoxylate, when CAT is inactive. ICL and its product appear to be sensitive to oxidative damage; thus, association of CAT with ICL would afford protection from H(2)O(2).
authors.affiliation: Department of Biological Sciences, The George Washington University, Lisner Hall, 2023 G St. NW #340, Washington, DC 20052, USA.
authors.forename: Tulin
authors.initials: T
authors.lastname: Yanik
authors.forename: Robert Paul
authors.initials: RP
authors.lastname: Donaldson
mesh_terms: D002367:Ricinus communis / Q000201:enzymology*; D002374:Catalase / Q000378:metabolism*; D002845:Chromatography; D004789:Enzyme Activation / Q000502:physiology; D006038:Glyoxylates / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007522:Isocitrate Lyase / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D020675:Peroxisomes / Q000201:enzymology*; D011485:Protein Binding; D012639:Seeds / Q000201:enzymology*
chemical_list: D006038:Glyoxylates; D006861:Hydrogen Peroxide; D002374:Catalase; D007522:Isocitrate Lyase; C031150:glyoxylic acid