Liver‐specific glucose‐6‐phosphatase is not present in human placenta

Abstract

Type I glycogen storage disease (McKusick 23220), an inherited absence or deficiency of glucose‐6‐phosphatase (EC 3.1.3.9) activity in the liver, kidney and intestine, is associated with the accumulation of glycogen in those organs. Previous reports have shown that glucose‐6‐phosphatase exists in human placenta and that detection of a heterozygote for this disorder from placenta might be possible. Our finding of a normal glucose‐6‐phosphatase activity in a placenta from a patient at risk for type Ia glycogen storage disease prompted us to examine in more detail placental glucose‐6‐phosphatase. Unexpectedly, we found the properties of the placental enzyme differed from that in normal liver, and the placental enzyme hydrolyzed glucose‐6‐phosphate, mannose‐6‐phosphate, β‐glycerol phosphate and glucose‐1‐phosphate equally well. Our data suggest the enzyme deficient in type I glycogen storage disease cannot be detected in placenta.