Search

El formaldehído es un agente citotóxico que provoca mutaciones in el DNA, ha sido clasificado como un carcinógeno. Se produce durante el metabolismo celular normal, pero su concentración aumenta con el estrés oxidativo. El formaldehído es un polucionante atmosférico (especialmente de interiores) y de aguas residuales. El principal sistema enzimático que metaboliza el formaldehído en los organismos eucariotas es mediante la formaldehído deshidrogenasa dependiente de glutatión. La formaldehído dehidrogenasa dependiente de glutatión, también, llamada ADH clase III, en presencia del NAD+ cataliza la oxidación de formaldehído. El sustrato real del enzima es el S-hidroximetilglutatión que se forma de la reacción espontánea entre el formaldehído y el glutatión. La FALDH se encuentra universalmente distribuida en todos los organismos, tanto en el reino vegetal como animal. Ambas propiedades del enzima, distribución ubicua y alta conservación de secuencia, sugieren que la función principal de este enzima es metabolismo del formaldehído tanto endógeno como exógeno.Se ha estudiado el efecto de sobreexpresión del gen de la FALDH en dos organismos Sacaromyces cerevisiae y Arabidopsis thaliana. La sobre expresión en un vector multicopias del gen FALDH en levadura confiere a ésta la capacidad de resistir a altas concentraciones de formaldehído (2 mM). También, se han obtenido varias plantas transgénicas que sobreexpresan la FALDH de Arabidopsis. El estudio de la capacidad de las diferentes líneas transgénicas de metabolizar concentraciones altas de formaldehído exógeno (5 mM y 2 mM), mostró un incremento del 20% y 30 % con respecto a plantas de Arabidopsis sin transformar. Aunque la sobreexpresión del gen, sin embargo, no impide que la exposición al formaldehído (5 mM) durante 24 H tendrá un efecto citotóxico, que produce la destrucción de los cloroplastos.De otra parte, la inmunolocalización de la FALDH en células de tabaco BY2, mostró que se encuentra en el citoplasma como en el núcleo. Su distribución es similar a la de la _-tubulina en las diferentes etapas del ciclo celular., Formaldehyde is cytotoxic agent that provokes mutations in DNA, and has been categorised as a carcinogen. It is produced during normal cellular metabolism, but its concentration increases by oxidative stress. Formaldehyde is also an important atmospheric pollant and a contaminant of risidual industrial waters. The main enzymatic system metabolising formaldehyde in eukaryotes is the gluthione-dependent formaldehyde dehydrogenase. The glutathione-dependent formaldehyde dehyrogenase (FALDH), also known as class III ADH, catalyzes the NAD+-dependent oxidation of formaldehyde. The true substrate of enzyme in this reaction is the S-hydroxymethylglutathione that forms spontaneously between formaldehyde and glutathione .The enzyme has a ubiquitous distribution in animals and plants, with constitutive levels of expresión, It has long been proposed that the primary function of this enzyme is to detoxify endogenous and exogenous formaldehyde.We have investigated the effects of overexpressing the FALDH gene in two living organisms, Saccharomyces cerevisiae and Arabidopsis thaliana. Overexpressing in yeatst confers high resístanse to formadehyde since the transformed strain is able to grow much better than the wild type strain at moderately hig concentration of this compound (2mM). Overexpressing in plants significantly increases their ability to eliminate high concentration of formaldeyde added exogeneeously to 20% and 30% en comparation with wild type. The rate of formaldehyde elimination is directly related to the amount of FALDH activity expressed by the plant. Tus confirming the essential role of this enzyme in the metabolism of formaldehyde. However, exposure to very high concentrations of formaldehyde (5mM) produces important phytotoxic effects both in the wild type and in transgenic arabidopsis plants,wich start to disply chlorotic lesions in the leaves after 24h of exposure. Examination by electronic microscopy revealed that those lesions were due to massive destruction of chloroplasts. These results open important issues for biotechnological aplications in the bioremediation of environmental formaldehyde.Also, we studied the subcellular localization of the enzyme in de tabacco BY2 cell line, and we demostrated the localization of FALDH in the cytoplasme and in the nucleus. The distribution of FALDH is identic to _-tubuline in diferentes phases of the cell cycle.

Arabidopsis thaliana was transformed with a plastidial safflower glycerol-3-phosphate acyltransferase (GPAT) and an Escherichia coli GPAT. The genes were used directly and in modified forms with, as applicable, the plastidial targeting sequence removed, and with an endoplasmic reticulum targeting sequence added. Seeds of plants transformed using only the vector were indistinguishable in oil content from wild-type control plants. All other gene constructs increased seed oil content. The unmodified safflower gene (spgpat) produced oil increases ranging from 10 to 21%. On average, the greatest increase (+22%) was observed in seeds of transformants carrying the spgpat with the targeting peptide removed. The E. coli plsB gene increased seed oil content by an average of 15%.