Kinetic and structural analysis of a new group of Acyl-CoA carboxylases found in Streptomyces coelicolor A3(2).
Two acyl-CoA carboxylases from Streptomyces coelicolor have been successfully reconstituted from their purified components. Both complexes shared the same biotinylated alpha subunit, AccA2. The beta and the epsilon subunits were specific from each of the complexes; thus, for the propionyl-CoA carboxylase complex the beta and epsilon components are PccB and PccE, whereas for the acetyl-CoA carboxylase complex the components are AccB and AccE. The two complexes showed very low activity in the absence of the corresponding epsilon subunits; addition of PccE or AccE dramatically increased the specific activity of the enzymes. The kinetic properties of the two acyl-CoA carboxylases showed a clear difference in their substrate specificity. The acetyl-CoA carboxylase was able to carboxylate acetyl-, propionyl-, or butyryl-CoA with approximately the same specificity. The propionyl-CoA carboxylase could not recognize acetyl-CoA as a substrate, whereas the specificity constant for propionyl-CoA was 2-fold higher than for butyryl-CoA. For both enzymes the epsilon subunits were found to specifically interact with their carboxyltransferase component forming a beta-epsilon subcomplex; this appears to facilitate the further interaction of these subunits with the alpha component. The epsilon subunit has been found genetically linked to several carboxyltransferases of different Streptomyces species; we propose that this subunit reflects a distinctive characteristic of a new group of acyl-CoA carboxylases.
Diacovich
Lautaro
L
Instituto de Biologia Molecular y Celular de Rosario (IBR-Consejo Nacional de Investigaciones Cientificas y Técnicas) and Departamento de Microbiologia, Universidad Nacional de Rosario, Suipaccha 531, 2000 Rosario, Argentina.
Peirú
Salvador
S
Kurth
Daniel
D
Rodríguez
Eduardo
E
Podestá
Florencio
F
Khosla
Chaitan
C
Gramajo
Hugo
H
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D019735:Carbon-Carbon Ligases / Q000737:chemistry* / Q000378:metabolism; D017124:Conserved Sequence; D007700:Kinetics; D008969:Molecular Sequence Data; D021122:Protein Subunits; D013302:Streptomyces / Q000201:enzymology*
D001426:Bacterial Proteins; D021122:Protein Subunits; D019735:Carbon-Carbon Ligases; C018757:acyl-CoA carboxylase; C022458:propionyl CoA carboxylase (ATP-hydrolyzing)