The function of GYG1 (glycogenin 1, Ensembl gene identifier ENSG00000163754) is as follows. Glycogenin participates in the glycogen biosynthetic process along with glycogen synthase and glycogen branching enzyme. It catalyzes the formation of a short alpha (1,4)-glucosyl chain covalently attached via a glucose 1-O-tyrosyl linkage to internal tyrosine residues and these chains act as primers for the elongation reaction catalyzed by glycogen synthase. {ECO:0000269|PubMed:22160680, ECO:0000269|PubMed:30356213}.