Mouse phosphoglycerate mutase M and B isozymes: cDNA cloning, enzyme activity assay and mapping.

Two mouse cDNAs encoding the non-muscle-specific or brain isoform (type B, Pgam1) and the muscle-specific isoform (type M, Pgam2) of phosphoglycerate mutase (PGAM) were isolated and characterized. Pgam1 contains a 765 bp open reading frame (ORF) coding for a 254-residue protein while Pgam2 contains a 762 bp ORF coding for a 253-residue protein. The deduced proteins of mouse Pgam1 and Pgam2 are highly similar to those of human and rat (> or = 93% similarity). Northern blot analysis showed that the expression patterns of Pgam1 and Pgam2 were distinct. Pgam1 was expressed as a 2.1-kb transcript highly in brain and kidney and moderately in liver, thyroid, stomach and heart, whereas Pgam2 was expressed as a 1.0-kb transcript highly in muscle, testis and moderately in heart and lung, but was not detectable in the other six tissues examined. Transfecting the cDNA fragments containing the entire ORFs of these two cDNAs into COS7 cells for transient expression, respectively, the enzyme activities of mouse Pgam1 and Pgam2 were detected to be 2.2-2.5 times of those of COS7 cells and COS7 cells transfected with vector, proving the validity of mouse Pgam1 and Pgam2 cDNAs we report here. Pgam1 and Pgam2 were assigned to 116.16 cR from D19Mit52 and 29.57 cR from D11Mit129, respectively, by radiation hybrid method. The partial genomic sequence of Pgam2 was determined, which showed that mouse Pgam2 consisted at least three exons and two introns. In addition, a pseudogene of Pgam1, Pgam1-ps1, was identified from mouse genomic sequence.