Characterisation and sequence analysis of a carbamate kinase gene from thediplomonad Hexamita inflata

Hexamita inflata can derive energy from the degradation of arginine via the arginine dihydrolase pathway. Carbamate kinase catalyses the third enzymat ic step of the pathway synthesising ATP from the catabolism of carbamyl pho sphate. This study reports the identification and characterisation of a car bamate kinase gene from this free-living diplomonad, together with measurem ents of carbamate kinase enzyme activity in cell-free extracts and a prelim inary analysis of the carbamate kinase mRNA by reverse-transcription polyme rase chain reaction. Analysis of the carbamate kinase gene revealed the use of non-canonical codons for glutamine. Phylogenetic studies showed a consi stent close relationship between carbamate kinase sequences of H. inflata a nd Giardia intestinalis.