Application of a controllable degron strategy for metabolic engineering

In numerous cases of metabolic engineering, metabolite pools have to be increased in order to obtain flux into heterologous pathways. A simple tool for this would be the deletion of genes that would practically lead to a block of the natural pathway, so that the carbon can flow into the heterologous pathway.

Unfortunately some deletions are lethal, as end products of pathways are needed for cellular growth. One example of such a pathway is the mevalonate pathway in S. cerevisiae with ergosterol as one of the most important end products. A great number of bioactive compounds, like various terpenoids, can be produced from intermediates of this pathway.

Different strategies have been applied in order to down-regulate the expression of enzymes involved in the mevalonate pathway. All these strategies work on the transcriptional level. This leads to a delay of the actual regulation, as the existing enzyme will still be active. We present a strategy for down-regulation that acts on the protein level and which can therefore be controlled in a more precise manner than the hitherto reported strategies.

As a case study we show the action of the degron strategy for controlling the pools of intermediates of the mevalonate pathway around 2,3-oxidosqualene, which is the precursor for triterpenoids. Many triterpenoids are pharmaceutically relevant compounds which nowadays need to be extracted from plant material through an intricate and resource consuming process.