Glucose-6-phosphatase in the insulin secreting cell line INS-1

The glucose-6-phosphatase system of the glucose sensitive insulin secreting rat insulinoma cells (INS-1) was investigated. INS-1 cells contain easily detectable levels of glucose-6-phosphatase enzyme protein (assessed by West ern blotting) and have a very significant enzymatic activity. The features of the enzyme (Km and Vmax values, sensitivity to acidic pH, partial latenc y, and double immunoreactive band) are similar to those of the hepatic form . On the other hand, hardly detectable levels of glucose-6-phosphatase acti vity and protein were present in the parent glucose insensitive RINm5F cell line. The mRNA of the glucose-6-phosphate transporter was also more abunda nt in the INS-1 cells. The results support the view that the glucose-6-phos phatase system of the p-cell is associated with the regulation of insulin s ecretion. (C) 2000 Academic Press.