TAILIEUCHUNG - Báo cáo khoa học: The physiologic role of alternative oxidase in Ustilago maydis

Alternative oxidase (AOX) is a ubiquitous respiratory enzyme found in plants, fungi, protists and some bacterial species. One of the major ques-tions about this enzyme is related to its metabolic role(s) in cellular physi-ology, due to its capacity to bypass the proton-pumping cytochrome pathway, and as a consequence it has great energy-wasting potential. | ỊFEBS Journal The physiologic role of alternative oxidase in Ustilago maydis Oscar Juarez1 Guadalupe Guerra2 Isabel Velazquez1 Oscar Flores-Herrera1 R. E. Rivera-Perez2 and Juan P. Pardo1 1 Departamento de Bioquimica Edificio D Facultad de Medicina Universidad NacionalAutonoma de Mexico 2 Departamento de Microbiologia Escuela Nacionalde Ciencias Biologicas IPN Casco de Santo Tomas Mexico Keywords alternative oxidase cyanide-insensitive respiration energy metabolism metabolic regulation reactive oxygen species ROS Correspondence J. P. Pardo Departamento de Bioquimica Facultad de Medicina Universidad Nacional Autonoma de Mexico Apartado postal 14080 Coyoacan Mexico . Mexico Fax 52 55 616 24 19 Tel 52 55 623 25 10 E-mail pardov@ Received 26 May 2006 revised 14 July 2006 accepted 11 August 2006 doi Alternative oxidase AOX is a ubiquitous respiratory enzyme found in plants fungi protists and some bacterial species. One of the major questions about this enzyme is related to its metabolic role s in cellular physiology due to its capacity to bypass the proton-pumping cytochrome pathway and as a consequence it has great energy-wasting potential. In this study the physiological role and regulatory mechanisms of AOX in the fungal phytopathogen Ustilago maydis were studied. We found evidence for at least two metabolic functions for AOX in this organism as a major part of the oxidative stress-handling machinery a well-described issue and as part of the mechanisms that increase the metabolic plasticity of the cell a role that might be valuable for organisms exposed to variations in temperature nutrient source and availability and biotic or abiotic factors that limit the activity of the cytochrome pathway. Experiments under different culture conditions of ecological significance for this organism revealed that AOX activity is modified by the growth stage of the culture amino acid availability and growth temperature. In addition .

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