The GAL3 regulatory function is required for rapid induction of the galactose system. At normal induction, galactose in the presence of the GAL3 protein may lead to the induction of the GAL genes, including GAL1. Then the galactokinase protein (GAL1) in the presence of galactose may reinforce the induction leading to a higher expression level. Upon depletion of galactose, the inducing activity of the galactokinase protein may decrease, after which transcription of the GAL genes, including GAL1, may decrease. The GAL3 gene is a member of the family of galactose inducible, glucose-repressible genes (which include GAL1, GAL2, GAL7, GAL10, GAL80, and MELI). Present with 721 molecules/cell in log phase SD medium. Belongs to the GHMP kinase family. GalK subfamily.