The PAS domain kinase PASKIN, also termed PAS kinase or PASK, is an evolutionarily conserved potential sensor kinase related to the heme-based oxygen sensors of nitrogen-fixing bacteria. In yeast, the two PASKIN homologs link energy flux and protein synthesis following specific stress conditions. In mammals, PASKIN may regulate glycogen synthesis and protein translation. Paskin knock-out mice do not show any phenotype under standard animal husbandry conditions. Interestingly, these mice seem to be protected from the symptoms of the metabolic syndrome when fed a high-fat diet. Energy turnover might be increased in specific PASKIN-deficient cell types under distinct environmental conditions. According to the current model, binding of a putative ligand to the PAS domain disinhibits the kinase domain and activates PASKIN auto- and target phosphorylation. Future research needs to be conducted to elucidate the nature of the putative ligand and the molecular mechanisms of downstream signalling by PASKIN.