Selective Phosphorylation of Phenols and Benzenediols by the Kinase PsiK and Variants Thereof

Phosphorylation plays important roles in biology by modulating the structure, reactivity, and biological function of a broad range of molecules. Biocatalytic phosphorylation has attracted attention from synthetic chemists due to its selectivity and mild reaction conditions using ATP as a phosphate donor. Given the potential synthetic utility of kinases with activity on small molecule substrates, we explored the activity of PsiK, the enzyme responsible for selective 4‐O‐phosphorylation of 4‐hydroxytryptamine or psilocin in psylocybin biosynthesis by Psilocybe cubensis. We find that PsiK has good activity on a range of substituted phenols and benzenediols beyond its native substrate, enabling preparative phosphorylation of different substrates, and substantially expands the substrate scope of biocatalytic phosphorylation. We also show that active site mutations can further expand substrate scope and improve site‐selectivity. This engineering effort was greatly expedited using DESI‐MS screening, which enabled analysis of 2,688 reactions in only 40 min. Finally, gram‐scale phosphorylation of a representative substrate was achieved with a turnover number over 10,000. Together, these results highlight the biocatalytic utility of PsiK and derivatives thereof for selective phosphorylation of phenols and benzenediols under mild conditions.