Regulation, characterization and factors affecting the amino acid transport systems

En esta revisión se describen los diferentes sistemas de transporte para aminoácidos, la caracterización de éstos y de sus componentes, los factores que afectan las características cinéticas de los acarreadores específicos de los sistemas de transporte, y la importancia del transporte de aminoácidos en el mantenimiento de las concentraciones plasmáticas e intracelulares de aminoácidos en diversos tejidos, así como su papel en el control del metabolismo de aminoácidos.

[Functional and evolutionary aspects of the aminoacyl-tRNA synthetases]. / Aspectos funcionales y evolutivos de las aminoacil-tRNA sintetasas.

A main event in protein bioshynthesis is the esterification of the correct aminoacid to cognate tRNA catalized by the aminoacyl-tRNA synthetases. The central role of this family of enzymes in metabolism is an evidence of their ancient origin. As it is the case in many others molecules involved in protein synthesis, the emergence of the aminoacyl-tRNA synthetases appears to be a problem that is not yet solved in order to understand the origin of the genetic translation. To obtain a comprehensive view of the evolution of the relationship between each one of the twenty aminoacyl-tRNA synthetases from one organism as well as from different sources (eubacteria, archaebacteria and eukaryotes) we review the information collected from the structural and catalytic properties of these enzyme. The results allow us to establish the following relationship between aminoacyl-tRNA synthetases. On one side there is a monofiletic origin for glutamyl, glutamynil and argynil-tRNA synthetases from Escherichia coli and for valyl, leucyl, metionyl, isoleucyl and phenylalanil-tRNA synthetases from eubacterias, archaebacterias and eukaryotes. On the other side there is an evolutionary relationship between aminoacyl-tRNA synthetases of eubacteria and organelles (plastids and mitochondria) and among eukaryotes and archaebacteria.