Characterisation of a Bi-functional Catalase-peroxidase of Burkholderia cenocepacia

Abstract

Isolates of Burkholderia cenocepacia express a putative haem-binding protein (Mr 97kDa) which displays intrinsic peroxidase activity. Its role has been re-evaluated, and we now show that it is a bi-functional catalase-peroxidase, with activity against tetramethylbenzidine (TMB), o-dianisidine, pyrogallol, and 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS). Both peroxidase and catalase activities are optimal at pH 5.5-6.0. The gene encoding this enzyme was cloned and expressed in E. coli. We have named it katG because of its similarity to other katGs including that from Burkholderia pseudomallei. It is substantially similar to a previously described catalase-peroxidase of B. cenocepacia (katA). Mass spectrometric analysis indicated that the initial katG translation product may be post-translationally modified in B. cenocepacia to give rise to the mature 97kDa catalase-peroxidase.