Regulation of the pyrimidine biosynthetic pathway by lysine acetylation of E. coli OPRTase

The de novo pyrimidine biosynthesis pathway is an important route due to the relevance of its products, its implications in health and its conservation among organisms. Here, we investigated the regulation by lysine acetylation of this pathway. To this aim, intracellular and extracellular metabolites of the route were quantified, revealing a possible blockage of the pathway by acetylation of the OPRTase enzyme (orotate phosphoribosyltransferase). Chemical acetylation of OPRTase by acetyl-P involved a decrease in enzymatic activity. To test the effect of acetylation in this enzyme, K26 and K103 residues were selected to generate site-specific acetylated proteins. Several differences were observed in kinetic parameters, emphasizing that the k(cat) of these mutants showed a strong decrease of 300 and 150-fold for OPRTase-103AcK and 19 and 6.3-fold for OPRTase-26AcK, for forward and reverse reactions. In vivo studies suggested acetylation of this enzyme by a nonenzymatic acetyl-P-dependent mechanism and a reversion of this process by the CobB deacetylase. A complementation assay of a deficient strain in the pyrE gene with OPRTase-26AcK and OPRTase-103AcK was performed, and curli formation, stoichiometric parameters and orotate excretion were measured. Complementation with acetylated enzymes entailed a profile very similar to that of the increment pyrE strain, especially in the case of complementation with OPRTase-103AcK. These results suggest regulation of the de novo pyrimidine biosynthesis pathway by lysine acetylation of OPRTase in Escherichia coli. This finding is of great relevance due to the essential role of this route and the OPRTase enzyme as a target for antimicrobial, antiviral and cancer treatments.

Automated summary

The regulation of the de novo pyrimidine biosynthesis pathway by lysine acetylation of the OPRTase enzyme was investigated in this study. It was found that acetylation of the OPRTase enzyme may block the pathway, leading to a decrease in enzymatic activity. Further experiments revealed that site-specific acetylation of the OPRTase enzyme resulted in significant changes in kinetic parameters. In vivo studies suggested that the acetylation of this enzyme is regulated by a nonenzymatic acetyl-P-dependent mechanism and can be reversed by the CobB deacetylase. Complementation assays showed that the expression of acetylated enzymes led to a profile similar to that of the increment pyrE strain, highlighting the importance of lysine acetylation in regulating the de novo pyrimidine biosynthesis pathway in Escherichia coli. These findings are of great relevance, as they provide insights into the essential role of this pathway and the potential for targeting the OPRTase enzyme in antimicrobial, antiviral, and cancer treatments.