PMM (PMM1), THE HUMAN HOMOLOG OF SEC53 OR YEAST PHOSPHOMANNOMUTASE, IS LOCALIZED ON CHROMOSOME 22Q13

We have cloned the human homologue of SEC53 or yeast phosphomannomutas e (HGMW-approved symbol PMM1) from a liver cDNA library, This cDNA enc odes a protein of 262 amino acids with a predicted molecular mass of 2 9 kDa and 54% identity with yeast phosphomannomutase, Expression of th e human cDNA in Escherichia coli yielded an active phosphomannomutase, which was purified to homogeneity. Northern blot analysis of human ti ssues showed strong expression in liver, heart, brain, and pancreas an d a lower expression in skeletal muscle, The gene was assigned to chro mosome 22113.1 by the use of hybrid cell lines and by fluorescence in situ hybridization. Most patients presenting with carbohydrate-deficie nt glycoprotein syndrome type 1 (CDG1 or Jaeken disease) have a greatl y reduced phosphomannomutase activity; the gene encoding this enzyme i s a likely candidate for CDG1 Since the CDG1 locus maps elsewhere in t he genome (16p13), mutations in the phosphomannomutase gene encoded by chromosome 22 are not a major cause of CDG1. (C) 1997 Academic Press.