Reconstitution of an Active Arginine Deiminase Pathway in Mycoplasma pneumoniae M129

Abstract

ABSTRACTSome species of the genusMycoplasmacode for the arginine deiminase pathway (ADI), which enables these bacteria to produce ATP from arginine by the successive reaction of three enzymes: arginine deiminase (ArcA), ornithine carbamoyltransferase (ArcB), and carbamate kinase (ArcC). It so far appears that independently isolated strains ofMycoplasma pneumoniaeencode an almost identical truncated version of the ADI pathway in which the proteins ArcA and ArcB have lost their original enzymatic activities due to the deletion of significant regions of these proteins. To study the consequences of a functional ADI pathway,M. pneumoniaeM129 was successfully transformed with the cloned functionalarcA,arcB, andarcCgenes fromMycoplasma fermentans. Enzymatic tests showed that while theM. pneumoniaeArcAB and ArcABC transformants possess functional arginine deiminase, ornithine carbamoyltransferase, and carbamate kinase, they were unable to grow on arginine as the sole energy source. Nevertheless, infection of a lung epithelial cell line, A549, with theM. pneumoniaetransformants showed that almost 100% of the infected host cells were nonviable, while most of the lung cells infected with nontransformedM. pneumoniaewere viable under the same experimental conditions.