A new variant of glycogen storage disease (GSD) Type 1, with clinical symptoms and laboratory findings consistent with those of glucose-6-phosphatase (G6Pase) deficiency, is described. Assay of G6Pase in liver from the patient immediately after biopsy by the method of Nordlie and Arion gave low activity (0.8 mumol/min per g liver) in the absence of detergent, but was normal (10.2 mumol/min per g liver) after addition of detergent. Liver stored for a day at -25 degrees C had normal activity (3.4 mumol/min per g liver) without detergent. In patients with GSD Type la, G6Pase activity was very low both with and without detergent. These findings suggest a defect in glucose-6-phosphate transport in the microsomal membrane of the patient's liver. The integrity of microsomal membrane was destroyed by storage at -25 degrees C, when activity of G6 ase in the patient's liver could be demonstrated. This may be the first example of a disorder involving the transport system of an intracellular membrane.
Patients with glycogen storage disease (GSD) type 1b have shown normal activity of glucose-6-phosphatase (EC 3.1.3.9) as assayed in frozen liver, though their clinical and biochemical findings were similar to those of patients with GSD 1a (McKusick 23220) (Senior and Loridan, 1968). In 1978, we suggested that a basic defect of GSD 1b exists in the glucose-6-phosphate (G6P) transport system (Narisawa et al., 1978; Igarashi et al., 1979). Since then, there have been reports confirming our observation (Beaudet et al., 1980; Lange et al., 1980; Corbeel et al., 1981; Schaub et al., 1981). Recently, it was postulated that the G6Pase system contains a phosphate translocase which mediates the efflux of phosphate, in addition to a G6P translocase and a non-specific phosphohydrolase (Arion et al., 1980). Therefore, it is possible that GSD 1b is caused by a defect of phosphate translocase. In this paper, the basic defect in GSD type 1b was investigated in two patients; one with severe, the other with mild, clinical symptoms.
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