Cloning, Expression, and Characterization of Para-Aminobenzoic Acid (PABA) Synthase from Agaricus bisporus 02, a Thermotolerant Mushroom Strain

Abstract

The pabS gene of Agaricus bisporus 02 encoding a putative PABA synthase was cloned, and then the recombinant protein was expressed in Escherichia coli BL21 under the control of the T7 promoter. The enzyme with an N-terminal GST tag or His tag, designated GST-AbADCS or His-AbADCS, was purified with glutathione Sepharose 4B or Ni Sepharose 6 Fast Flow. The enzyme was an aminodeoxychorismate synthase, and it was necessary to add with an aminodeoxychorismate lyase for synthesizing PABA. AbADCS has maximum activity at a temperature of approximately 25°C and pH 8.0. Magnesium or manganese ions were necessary for the enzymatic activity. The Michaelis-Menten constant for chorismate was 0.12 mM, and 2.55 mM for glutamine. H2O2 did distinct damage on the activity of the enzyme, which could be slightly recovered by Hsp20. Sulfydryl reagents could remarkably promote its activity, suggesting that cysteine residues are essential for catalytic function.

Para-aminobenzoic acid synthase from mushroom Agaricus bisporus enhances UV-C tolerance in Arabidopsis by reducing oxidative DNA damage

“…In our study, Pabs overexpressing Arabidopsis was less susceptible to UV-C than Col proved by relative primary root elongation assay and the morphogenic responses. Pabs gene was previously proved to be the key enzyme of PABA synthesis in vitro (Deng et al 2015). While low concentrations of 0.02 mM PABA could slightly increase root length, high concentrations of PABA (more than 0.1 mM) could significantly inhibit the primary root growth of Arabidopsis seedlings (Crisan et al 2014).…”