One of the three SNF1 protein kinases (with SAK1 and ELM1) which are required for growth on nonfermentable carbon sources and nonpreferred sugars and for response to environmental stress. Activates SNF1 by phosphorylation of its activation-loop 'Thr-210'. Required for the regulation by SNF1 of the transcription of a large set of genes, the modification the activity of metabolic enzymes, and the control of various nutrient-responsive cellular developmental processes. Phosphorylates also GAL83, MIG1 and SIP2 (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] The C-terminus (residues 351 to 560) is required for efficient SNF1 pathway signaling. Autophosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.