Hydrolyzes glucose-6-phosphate to glucose in the endoplasmic reticulum. Forms with the glucose-6-phosphate transporter (SLC37A4/G6PT) the complex responsible for glucose production in the terminal step of glycogenolysis and gluconeogenesis. Hence, it is the key enzyme in homeostatic regulation of blood glucose levels. {ECO:0000269|PubMed:10960498, ECO:0000269|PubMed:12093795, ECO:0000269|PubMed:15542400, ECO:0000269|PubMed:9332655, ECO:0000269|PubMed:9497333}. This is the function of Ensembl gene identifier ENSG00000131482 (G6PC1, glucose-6-phosphatase catalytic subunit 1).