Abstract
Glycogen-filled vacuoles (glycogenosomes) were ubiquitously observed in hepatocytes of masu salmon (Oncorhynchus masou), mimicking the cytology of human glycogen storage disease type II (GSD II) with an inherited deficiency of lysosomal acid α-glucosidase (AAG). We re-examined the relationship between α-glucosidase activities and appearance of glycogenosomes in the fish. The fish liver AAG activity measured at pH 4.5 with glycogen as the substrate was comparable to that of mouse liver. However, we observed that neutral α-glucosidase (NAG) activity measured at pH 6.5 was significantly lower than that in mouse liver. These results suggest that the formation of glycogeno-somes is associated with NAG deficiency, similar to the late-onset adult form of GSD II.
