Probable G protein-coupled receptor that may be activated by a major product of dietary fiber digestion, the short chain fatty acids (SCFAs), and that may play a role in the regulation of whole-body energy homeostasis and/or in intestinal immunity. Was originally thought to be a pseudogene due to the presence of a Trp at position 174 which prevents activation by short chain fatty acids, such as propionate (PubMed:12496283). However, the inactivating Trp-174 that differentiate GPR42 from the homologous functional G-protein-coupled receptor FFAR3 is most probably polymorphic for both genes in the human population. The frequency of the active allele of GPR42, with Arg at position 174, is estimated to 61%. Moreover, the 5 other amino acid differences at positions 44, 45, 227, 256 and 346 between GPR42 and FFAR3, are also polymorphic in the human population (PubMed:19630535). Belongs to the G-protein coupled receptor 1 family.