Coenzyme A-transferase that converts butyryl-CoA to butyrate. Can also use proprionyl-CoA as substrate in vitro. acetyl-CoA + butanoate = acetate + butanoyl-CoA acetyl-CoA + propanoate = acetate + propanoyl-CoA Optimum pH is 7-8. Lipid metabolism; butanoate metabolism. The fermentation acid butyrate is of special interest, as it has been shown to serve as the preferred energy source for the gut wall and also influences cell differentiation and apoptosis in the colon, and this seems to aid in protection against colon cancer and inflammatory bowel disease. Formation of butyrate via butyryl-CoA CoA-transferase is the only available route for butyrate synthesis in the majority of human gut isolates. Belongs to the acetyl-CoA hydrolase/transferase family. Butyryl-CoA CoA-transferase subfamily.