Catalyzes the reversible formation of acetate and ATP from acetyl-CoA by using ADP and phosphate. Can use other substrates such as isobutyryl-CoA, propionyl-CoA and butyryl-CoA, but not indoleacetyl-CoA, phenylacetyl-CoA or succinyl-CoA. Seems to be involved primarily in the conversion of acetyl-CoA to acetate. Participates in the degradation of branched-chain amino acids via branched-chain-acyl-CoA esters. acetate + ATP + CoA = acetyl-CoA + ADP + phosphate Activity is dependent on magnesium. kcat is 203 sec(-1) for ADP. kcat is 411 sec(-1) for GDP. kcat is 182 sec(-1) for phosphate. kcat is 157 sec(-1) for acetyl-CoA. kcat is 121 sec(-1) for isobutyryl-CoA. kcat is 82 sec(-1) for ATP. kcat is 121 sec(-1) for GTP. kcat is 73 sec(-1) for CoA. kcat is 65 sec(-1) for acetate. kcat is 55 sec(-1) for isobutyrate. Optimum pH is 9.0 (at 80 degrees Celsius) (PubMed:8830684). Optimum pH is 7.0 (at 55 degrees Celsius) (PubMed:9119024). Optimum temperature is above 90 degrees Celsius. Heterotetramer of two alpha and two beta subunits. Belongs to the acetate CoA ligase beta subunit family.