Identification of the Pseudomonas aeruginosa glmM gene, encoding phosphoglucosamine mutase

A search for a potential algC homologue within the Pseudomonas aeruginosa PAO1 genome database has revealed an open reading frame (ORF) of unknown function, ORF540 in contig 54 (July 1999 Pseudomonas genome release), that theoretically coded for a 445-amino-acid-residue polypeptide (I. M. Tavares, J. H. Leitão, A. M. Fialho, and I. Sá-Correia, Res. Microbiol. 150:105-116, 1999). The product of this gene is here identified as the phosphoglucosamine mutase (GlmM) which catalyzes the conversion of glucosamine-6-phosphate to glucosamine-1-phosphate, an essential step in the formation of the cell wall precursor UDP-N-acetylglucosamine. The P. aeruginosa gene has been cloned into expression vectors and shown to restore normal peptidoglycan biosynthesis and cell growth of a glmM Escherichia coli mutant strain. The GlmM enzyme from P. aeruginosa has been overproduced to high levels and purified to homogeneity in a six-histidine-tagged form. Beside its phosphoglucosamine mutase activity, the P. aeruginosa enzyme is shown to exhibit phosphomannomutase and phosphoglucomutase activities, which represent about 20 and 2% of its GlmM activity, respectively.