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

Hexamita inflata can derive energy from the degradation of arginine via the arginine dihydrolase pathway. Carbamate kinase catalyses the third enzymatic step of the pathway synthesising ATP from the catabolism of carbamyl phosphate. This study reports the identification and characterisation of a carbamate kinase gene from this free-living diplomonad, together with measurements of carbamate kinase enzyme activity in cell-free extracts and a preliminary analysis of the carbamate kinase mRNA by reverse-transcription polymerase chain reaction. Analysis of the carbamate kinase gene revealed the use of non-canonical codons for glutamine. Phylogenetic studies showed a consistent close relationship between carbamate kinase sequences of H. inflata and Giardia intestinalis.