Formation of 4-hydroxybenzoate in Escherichia coli: characterization of the ubiC gene and its encoded enzyme chorismate pyruvate-lyase

Abstract

Chorismate pyruvate-lyase from Escherichia coli converts chorismate to 4-hydroxybenzoate. The enzyme was enriched 3000-fold by overexpression and chromatographic purification. It has an apparent Km value for chorismate of 6.1 microM and an isoelectric point of pH 6.45. The enzyme activity did not require metal cofactors. Promoter sequences in the 5' flanking sequences of the ubiCA operon were localized by transcription and translation of active chorismate pyruvate-lyase in vitro from different PCR fragments. Sequencing of the ubiC gene of the mutant strain AN244 revealed a G-->A transition resulting in a change from glutamic acid to lysine. A feeding experiment with [1,7-13C2]shikimate confirmed the chorismate pyruvate-lyase as the sole enzymic source of 4-hydroxybenzoate in vivo.