RESUMO
Based on the primary structure of the rat peroxisomal 2,4-dienoyl-CoA reductase (M. Fransen, P.P. Van Veldhoven, S. Subramani, Biochem. J. 340 (1999) 561-568), the cDNA of the human counterpart was cloned. It contained an open reading frame of 878 bases encoding a protein of 291 amino acids (calculated molecular mass 30778 Da), being 83% identical to the rat reductase. The gene, encompassing nine exons, is located at chromosome 16p13. Bacterially expressed poly(His)-tagged reductase was active not only towards short and medium chain 2,4-dienoyl-CoAs, but also towards 2,4,7,10,13,16,19-docosaheptaenoyl-CoA. Hence, the reductase does not seem to constitute a rate limiting step in the peroxisomal degradation of docosahexaenoic acid. The reduction of docosaheptaenoyl-CoA, however, was severely decreased in the presence of albumin.
Assuntos
Ácidos Graxos Dessaturases/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH , Peroxissomos/enzimologia , Acil Coenzima A/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , DNA Complementar/biossíntese , DNA Complementar/química , Ácidos Docosa-Hexaenoicos/metabolismo , Ácidos Graxos Dessaturases/biossíntese , Ácidos Graxos Dessaturases/química , Humanos , Cinética , Dados de Sequência MolecularRESUMO
The purpose of this study was to investigate whether deficient peroxisomal beta-oxidation is causally involved in the neuronal migration defect observed in Pex5 knockout mice. These mice are models for Zellweger syndrome, a peroxisome biogenesis disorder. Neocortical development was evaluated in mice carrying a partial or complete defect of peroxisomal beta-oxidation at the level of the second enzyme of the pathway, namely, the hydratase-dehydrogenase multifunctional/bifunctional enzymes MFP1/L-PBE and MFP2/D-PBE. In contrast to patients with multifunctional protein 2 deficiency who present with neocortical dysgenesis, impairment of neuronal migration was not observed in the single MFP2 or in the double MFP1/MFP2 knockout mice. At birth, the double knockout pups displayed variable growth retardation and about one half of them were severely hypotonic, whereas the single MFP2 knockout animals were all normal in the perinatal period. These results indicate that in the mouse, defective peroxisomal beta-oxidation does not cause neuronal migration defects by itself. This does not exclude that the inactivity of this metabolic pathway contributes to the brain pathology in mice and patients with complete absence of functional peroxisomes.
Assuntos
Movimento Celular/fisiologia , Neurônios/metabolismo , Peroxissomos/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Síndrome de Zellweger/enzimologia , Animais , Química Encefálica , Células Cultivadas , Córtex Cerebral/citologia , Córtex Cerebral/enzimologia , Córtex Cerebral/metabolismo , Modelos Animais de Doenças , Ácidos Graxos/metabolismo , Fibroblastos/metabolismo , Camundongos , Camundongos Endogâmicos , Camundongos Knockout , Oxirredução , Receptor 1 de Sinal de Orientação para Peroxissomos , Receptores Citoplasmáticos e Nucleares/metabolismo , Síndrome de Zellweger/genética , Síndrome de Zellweger/fisiopatologiaRESUMO
AIMS: Tamoxifen is widely used in the treatment of breast cancer. It is a pro-drug metabolized to the more active endoxifen through CYP2D6. Concomitant intake of CYP2D6 inhibitors results in lower endoxifen levels and could influence efficacy. The objective of this study was to evaluate the evolution of co-prescription of tamoxifen and CYP2D6 inhibitors in Belgium. METHODS: Data were retrieved from the Pharmanet database of the National Institute for Health and Disability Insurance for the period January 2006-December 2009. For the analysis of the evolution of the co-prescription, the period was divided in subperiods of 2 months. The category tamoxifen+CYP2D6 inhibitor was defined as women who were delivered tamoxifen and a CYP2D6 inhibitor in that subperiod. The results were validated on the period December 2011-May 2012. RESULTS: The percentage of co-prescription decreased over time for the strong CYP2D6 inhibitors and increased for the weak CYP2D6 inhibitor, with these trends persisting in 2012. Tamoxifen and CYP2D6 inhibitors were mostly prescribed by general practitioners and gynaecologists and by general practitioners and psychiatrists, respectively. DISCUSSION: This study shows that a proportion of women taking tamoxifen in Belgium are prescribed a strong CYP2D6 inhibitor, which could affect tamoxifen efficacy. Over time, the concomitant intake decreased. Paroxetine was the most prescribed strong CYP2D6 inhibitor. Venlafaxine, a weak CYP2D6 inhibitor, was prescribed more often. This study also shows that tamoxifen and the CYP2D6 inhibitors are not only prescribed by physicians specialized in breast cancer; therefore, all physicians should be aware of this interaction.
Assuntos
Antidepressivos de Segunda Geração/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Inibidores do Citocromo P-450 CYP2D6 , Padrões de Prática Médica/estatística & dados numéricos , Tamoxifeno/uso terapêutico , Antidepressivos de Segunda Geração/metabolismo , Bélgica , Bupropiona/metabolismo , Bupropiona/uso terapêutico , Cicloexanóis/metabolismo , Cicloexanóis/uso terapêutico , Quimioterapia Combinada , Feminino , Fluoxetina/metabolismo , Fluoxetina/uso terapêutico , Humanos , Paroxetina/metabolismo , Paroxetina/uso terapêutico , Resultado do Tratamento , Cloridrato de VenlafaxinaRESUMO
2-Methylacyl-CoA racemase is an auxiliary enzyme required for the peroxisomal beta-oxidative breakdown of (2R)-pristanic acid and the (25R)-isomer of C(27) bile acid intermediates. The enzyme activity is found not only in peroxisomes but also is present in mitochondria of human liver and fibroblasts. The C terminus of the human racemase, a protein of 382 amino acids with a molecular mass of 43,304 daltons as deduced from its cloned cDNA, consists of KASL. Hitherto this sequence has not been recognized as a peroxisomal targeting signal (PTS1). From the in vitro interaction between recombinant racemase and recombinant human PTS1 receptor (Pex5p), and the peroxisomal localization of green fluorescent protein (GFP) fused to the N terminus of full-length racemase or its last six amino acids in tranfected Chinese hamster ovary (CHO) cells, we concluded that ASL is a new PTS1 variant. To be recognized by Pex5p, however, the preceding lysine residue is critical. As shown in another series of transfection experiments with GFP fused to the C terminus of the full-length racemase or racemase with deletions of the N terminus, mitochondrial targeting information is localized between amino acids 22 and 85.Hence, our data show that a single transcript gives rise to a racemase protein containing two topogenic signals, explaining the dual cellular localization of the activity.