Hydrolyzes glucose-6-phosphate to glucose in the endoplasmic reticulum. May form with the glucose-6-phosphate transporter (SLC37A4/G6PT) a ubiquitously expressed complex responsible for glucose production through glycogenolysis and gluconeogenesis. Probably required for normal neutrophil function. {ECO:0000269|PubMed:12370122, ECO:0000269|PubMed:12965222, ECO:0000269|PubMed:13129915}. This is the function of G6PC3 (glucose-6-phosphatase catalytic subunit 3, ENSG00000141349).