MOLECULAR ABNORMALITY OF A PHOSPHOGLYCERATE KINASE VARIANT (PGK-ALABAMA)

The molecular abnormality of a phosphoglycerate kinase variant associa ted with severe red cell enzyme deficiency (about 4% of normal) and ep isodes of hemolysis with jaundice was examined. The Michaelis constant s for the substrates and co-enzymes (1,3-diphosphoglycerate, 3-phospho glycerate, ATP and ADP) were not grossly different from that of normal . However, the variant enzyme was very labile in vitro. Nucleotide seq uence analysis of the variant cDNA revealed a deletion of codon AAG in exon 7. The codon deletion should result in the deletion of one of th e tandem lysine residues existing at amino acid 190-191 of the enzyme protein. Based on the three dimensional structure of the protein, mole cular instability could be induced by the deletion of a lysine residue .