title: Activity of the mitochondrial pyruvate dehydrogenase complex in plants is stimulated in the presence of malate.
abstract: The effect of malate on the steady-state activity of the pea (Pisum sativum L.) and barley (Hordeum vulgare L.) leaf pyruvate dehydrogenase complex (PDC) has been studied in isolated mitochondria. The addition of malate was found to be stimulatory for the mitochondrial PDC, however there was no stimulation of chloroplast PDC. The stimulation was saturated below 1mM malate and was apparently related to а partially activated complex, which activity increased in the presence of malate by about twofold. Malate also reversed the reduction of PDC activity in the presence of glycine. Based on the obtained kinetic data, we suggest that the effect of malate is rather not a direct activation of PDC but involves the establishment of NAD-malate dehydrogenase equilibrium, decreasing concentration of NADH and relieving its inhibitory effect of PDC.
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada. Electronic address: igamberdiev@mun.ca.
authors.forename: Abir U
authors.initials: AU
authors.lastname: Igamberdiev
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, University of Umeå, SE-901 87 Umeå, Sweden.
authors.forename: Ulrikа
authors.initials: U
authors.lastname: Lernmark
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, University of Umeå, SE-901 87 Umeå, Sweden. Electronic address: per.gardestrom@umu.se.
authors.forename: Per
authors.initials: P
authors.lastname: Gardeström
mesh_terms: D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005998:Glycine / Q000378:metabolism; D001467:Hordeum / Q000201:enzymology*; D007700:Kinetics; D008293:Malates / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D018532:Pisum sativum / Q000201:enzymology*; D018515:Plant Leaves / Q000201:enzymology; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*
chemical_list: D008293:Malates; D011768:Pyruvate Dehydrogenase Complex; D009243:NAD; C030298:malic acid; D005998:Glycine
keywords: Glycine; Malate dehydrogenase; Photorespiration; Plant mitochondria; Pyruvate dehydrogenase complex