[Beta]-Hydroxylation of the aspartyl residue in the phytotoxin syringomycin E: characterization of two candidate hydroxylases AspH and SyrP in Pseudomonas syringae

A study is conducted to evaluate the catalytic function and activity of AspH in Escherichia coli, the capacity of AspH to hydroxylate free Asp vs Asp in thioester linkage and also determine the chirality of [beta]-hydroxylation. The aspartyl hydroxylase is observed to generate only the threo-3-OH-Asp product that is involved in syringomycin maturation.