Mechanistic investigation of a D to N mutation in DAHP synthase that dictates carbon flux into the shikimate pathway in yeast

Abstract

3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) is a key enzyme in the shikimate pathway for the biosynthesis of aromatic compounds. _L-Phe and _L-Tyr bind to the two main DAHPS isoforms and inhibit their enzyme activities, respectively. Synthetic biologists aim to relieve such inhibitions in order to improve the productivity of aromatic compounds. In this work, we reported a point mutant of yeast DHAPS, Aro3^D154N, which retains the wild type enzyme activity but converts it highly inert to the inhibition by _L-Phe. The Aro3 crystal structure along with the molecular dynamics simulations analysis suggests that the D154N mutation distant from the inhibitor binding cavity may reduce the binding affinity of _L-Phe. Growth assays demonstrated that substitution of the conserved D154 with asparagine suffices to relieve the inhibition of _L-Phe on Aro3, _L-Tyr on Aro4, and the inhibitions on their corresponding homologues from diverse yeasts. The importance of our discovery is highlighted by the observation of 29.1% and 43.6% increase of yield for the production of tyrosol and salidroside respectively upon substituting ARO3 with ARO3^D154N. We anticipate that this allele would be used broadly to increase the yield of various aromatic products in metabolically diverse microorganisms.

3-Deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) is a key enzyme in the shikimate pathway for the biosynthesis of aromatic compounds, however, its activity is inhibited by L-Phe and L-Tyr. Here, the authors report the D154N point mutation of yeast DAHPS, which retains the wild type enzyme activity but relieves the inhibition by L-Phe, thus increasing the production of downstream aromatic amino acid derivatives.