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Kinetic and Structural Analysis of a New Group of Acyl-CoA Carboxylases Found in Streptomyces coelicolor A3(2)

2002; Elsevier BV; Volume: 277; Issue: 34 Linguagem: Inglês

10.1074/jbc.m203263200

1083-351X

Lautaro Diacovich, Salvador Peirú, Daniel Kurth, Eduardo Rodrı́guez, Florencio E. Podestá, Chaitan Khosla, Hugo Gramajo,

Microbial Natural Products and Biosynthesis

Two acyl-CoA carboxylases from Streptomyces coelicolor have been successfully reconstituted from their purified components. Both complexes shared the same biotinylated α subunit, AccA2. The β and the ε subunits were specific from each of the complexes; thus, for the propionyl-CoA carboxylase complex the β and ε 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 ε 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 ε subunits were found to specifically interact with their carboxyltransferase component forming a β-ε subcomplex; this appears to facilitate the further interaction of these subunits with the α component. The ε 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.