Enzymic characterization of a novel member of the regulatory B-like carboxypeptidase with transcriptional repression function: stimulation of enzymicactivity by its target DNA

The adiyocyte-enhancer binding protein (AEBP) 1 is a novel transcriptional repressor with carboxypeptidase (CP) activity. AEBP1 binds to a regulatory sequence (termed adipocyte enhancer 1, AE-1) located in the proximal promot er region of the adipose P2(aP2) gene, which encodes the adipocyte fatty-ac id binding protein. Sequence comparisons and kinetic studies using known ca rboxypeptidase substrates, activators and inhibitors have characterized AEB P1 as a member of the regulatory B-like CP family: Significantly, the inher ent CP activity of AEBP1 is stimulated by the AE-1 sequence. Our results in dicate that AEBP1 is activated by a novel mechanism, wherby the direct bind ing of DNA enhances its protease activity. These results represent the firs t demonstration of DNA-mediated regulation of CP activity.