A DIFFERENT ISOFORM OF THE TRANSPORT PROTEIN MUTATED IN THE GLYCOGEN-STORAGE-DISEASE 1B IS EXPRESSED IN BRAIN

There are differences in the kinetic properties of the liver and brain microsomal glucose-6-phosphate transport systems suggesting the possi bility of tissue specific isoforms. The availability of a human liver cDNA sequence which is mutated in patients with deficiencies of liver microsomal glucose-6-phosphate transport (glycogen storage disease 1b) made it possible to determine if a brain isoform exists. Northern blo ts of liver and brain RNA revealed that the mRNA of the brain form is slightly longer than the liver one. Isolation and sequencing of the re spective human brain cDNA revealed that the brain protein has an addit ional 22 amino acid sequence. (C) 1998 Federation of European Biochemi cal Societies.