Comparison of the stability and substrate specificity of purified peroxisomal 3-oxoacyl-CoA thiolases A and B from rat liver

The specific activities and substrate specificities of 3-oxoacyl-CoA thiola se A (thiolase A) purified from normal rat liver peroxisomes and 3-oxoacyl- CoA thiolase B (thiolase B) isolated from livers of rats treated with the p eroxisome proliferator clofibrate were virtually identical. The enzymes cou ld be distinguished by their N-terminal amino acid sequences, their isoelec tric points and their stability, the latter being higher for thiolase A. Co ntrary to thiolase B, which showed a marked cold lability in the presence o f KCI by dissociating into monomers with Door activity, thiolase A retained its full activity and its homodimeric structure under these conditions. (C ) 1999 Elsevier Science B,V. All rights reserved.