RESUMEN
The ICL1 gene encoding isocitrate lyase was cloned from the dimorphic fungus Yarrowia lipolytica by complementation of a mutation (acuA3) in the structural gene of isocitrate lyase of Escherichia coli. The open reading frame of ICL1 is 1668 bp long and contains no introns in contrast to currently sequenced genes from other filamentous fungi. The ICL1 gene encodes a deduced protein of 555 amino acids with a molecular weight of 62 kDa, which fits the observed size of the purified monomer of isocitrate lyase from Y. lipolytica. Comparison of the protein sequence with those of known pro- and eukaryotic isocitrate lyases revealed a high degree of homology among these enzymes. The isocitrate lyase of Y. lipolytica is more similar to those from Candida tropicalis and filamentous fungi than to Saccharomyces cerevisiae. This enzyme of Y. lipolytica has the putative glyoxysomal targeting signal S-K-L at the carboxy-terminus. It contains a partial repeat which is typical for eukaryotic isocitrate lyases but which is absent from the E. coli enzyme. Surprisingly, deletion of the ICL1 gene from the genome not only inhibits the utilization of acetate, ethanol, and fatty acids, but also reduces the growth rate on glucose.
Asunto(s)
Proteínas Fúngicas/genética , Genes Fúngicos , Isocitratoliasa/genética , Saccharomycetales/genética , Secuencia de Aminoácidos , Secuencia de Bases , Northern Blotting , Clonación Molecular , ADN de Hongos , Proteínas Fúngicas/metabolismo , Intrones , Isocitratoliasa/metabolismo , Datos de Secuencia Molecular , Peso Molecular , Sistemas de Lectura Abierta , Mapeo Restrictivo , Saccharomycetales/enzimología , Homología de Secuencia de Aminoácido , Transformación GenéticaRESUMEN
In an experimental investigation of 20 subjects who had no amalgam fillings, the mercury load from artificially applied, standardised amalgam surfaces was tested for one product containing gamma-2 and one free of gamma-2 respectively. The product which contained gamma-2 caused a statistically significant increase in Hg concentrations in the 24-hour urine sample. After challenge with Dimaval, an intensifying effect on the elimination rate could be detected, although all values clearly remained below a toxicologically relevant concentration. In order to avoid unnecessary exposure to heavy metals, the use of gamma-2-free amalgams and, in the long term, the development of optimised filling materials and intensification of prophylactic measures for prevention of dental caries are to be welcomed.