Evolution von Stoffwechselwegen bei Mikroorganismen

Abstract

Research on the evolution of new metabolic pathways in microorganisms is challenged by two fields of current interest: Enzyme engineering and accumulation of some man-made chemicals in the biosphere. On theoretical grounds it is assumed that metabolic pathways have evolved in a retrograde manner by a stepwise process of tandem gene duplication and subsequent divergence of gene function. Some steps of this process have been studied by analyzing the evolution of new enzymatic activities in catabolic pathways of bacteria. In studies on the acquisition of xylitol utilization in Aerobacter aerogenes and on the directed evolution of the aliphatic amidase of Pseudomonas aeruginosa new metabolic activities were related to defined changes in enzymes and regulatory systems. The evolution of biosynthetic pathways is not amenable to experiments but has been studied by comparative biochemistry. While biosynthetic pathways seem to be similar in widely divergent microorganisms the regulatory patterns may be very different. This general observation is illustrated by comparing the regulation of arginine biosynthesis in Escherichia coli and Pseudomonas aeruginosa.