title: Inhibition of mitochondrial creatine kinase activity from rat cerebral cortex by methylmalonic acid.
abstract: Accumulation of methylmalonic acid (MMA) in tissues and biological fluids is the biochemical hallmark of patients affected by the neurometabolic disorder known as methylmalonic acidemia (MMAemia). Although this disease is predominantly characterized by severe neurological findings, the underlying mechanisms of brain injury are not totally established. In the present study, we investigated the effect of MMA, as well as propionic (PA) and tiglic (TA) acids, whose concentrations are also increased but to a lesser extend in MMAemia, on total (tCK), cytosolic (Cy-CK) and mitochondrial (Mi-CK) creatine kinase (CK) activities from cerebral cortex of 30-day-old Wistar rats. Total CK activity (tCK) was measured in whole cell homogenates, whereas Cy-CK and Mi-CK were determined, respectively, in cytosolic and mitochondrial preparations from rat cerebral cortex. We verified that tCK and Mi-CK activities were significantly inhibited by MMA at concentrations as low as 1 mM, in contrast to Cy-CK which was not affected by the presence of the acid in the incubation medium. Furthermore, PA and TA, at concentrations as high as 5 mM, did not alter CK activity. We also observed that the inhibitions provoked by MMA were fully prevented by pre-incubation of the homogenates with reduced glutathione, suggesting that the inhibitory effect of MMA was possibly mediated by oxidation of essential thiol groups of the enzyme. Considering the importance of CK for brain metabolism homeostasis, our results suggest that inhibition of this enzyme by increased levels of MMA may contribute to the neurodegeneration of patients affected by MMAemia and explain previous reports showing an impairment of brain energy metabolism and a reduction of brain phosphocreatine levels caused by MMA.
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600 Anexo, CEP 90035-003, Porto Alegre, RS, Brazil.
authors.forename: P F
authors.initials: PF
authors.lastname: Schuck
authors.forename: R B
authors.initials: RB
authors.lastname: Rosa
authors.forename: L F
authors.initials: LF
authors.lastname: Pettenuzzo
authors.forename: A
authors.initials: A
authors.lastname: Sitta
authors.forename: C M D
authors.initials: CM
authors.lastname: Wannmacher
authors.forename: A T S
authors.initials: AT
authors.lastname: Wyse
authors.forename: M
authors.initials: M
authors.lastname: Wajner
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology*; D003402:Creatine Kinase / Q000037:antagonists & inhibitors*; D003437:Crotonates / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D045782:Hemiterpenes; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008297:Male; D008764:Methylmalonic Acid / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052248:Nitric Oxide Synthase Type I; D011422:Propionates / Q000494:pharmacology; D051381:Rats
chemical_list: D000975:Antioxidants; D003437:Crotonates; D004791:Enzyme Inhibitors; D045782:Hemiterpenes; D007202:Indicators and Reagents; D009419:Nerve Tissue Proteins; D011422:Propionates; D008764:Methylmalonic Acid; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D003402:Creatine Kinase; C009489:tiglic acid; C029658:propionic acid