LIVER MICROSOMAL TRANSPORT OF GLUCOSE-6-PHOSPHATE, GLUCOSE, AND PHOSPHATE IN TYPE-1 GLYCOGEN-STORAGE DISEASES

The transport of glucose-6-phosphate (G6P), glucose, and orthophosphat e into liver microsomes, isolated from six patients with various subty pes of type 1 glycogen storage disease (GSD), was measured using a lig ht-scattering method. We found that G6P, glucose, and phosphate could all cross the microsomal membrane, in four cases of type la GSD. In co ntrast, liver microsomal transport of G6P and phosphate was deficient in the GSD Ib and Ic patients, respectively. These results support the involvement of multiple proteins (and genes) in GSD type 1. The resul ts obtained with the light-scattering method are in accordance with co nventional kinetic analysis of the microsomal glucose-6-phosphatase sy stem. Therefore, this technique could be used to directly diagnose typ e Ib and Ic GSD.