tailieunhanh - Báo cáo khoa học: A characteristic Glu17 residue of pig carnitine palmitoyltransferase 1 is responsible for the low Km for carnitine and the low sensitivity to malonyl-CoA inhibition of the enzyme

Human carnitine palmitoyltransferase 1B (CPT1B) is a highly malonyl-CoA-sensitive enzyme (IC50 = ) and has a positive determinant (residues 18–28) of malonyl-CoA inhibition. By contrast, rat carnitine palmitoyltransferase 1A is less sensitive to malonyl-CoA inhibition (IC50= ), and has both a positive (residues 1–18) and a negative (residues 18–28) determinant of its inhibition. | ễFEBS Journal A characteristic Glu17 residue of pig carnitine palmitoyltransferase 1 is responsible for the low Km for carnitine and the low sensitivity to malonyl-CoA inhibition of the enzyme Joana Relat Magdalena Pujol-Vidal Diego Haro and Pedro F. Marrero Department of Biochemistry and Molecular Biology Schoolof Pharmacy and Institute of Biomedicine of Barcelona University IBUB Spain Keywords carnitine affinity fatty acid oxidation human CPT1B malonyl-CoA inhibition pig CPT1B Correspondence P. F. Marrero Departamento de Bioquimica y Biologia Molecular Facultad de Farmacia Universidad de Barcelona Diagonal643 08028 E-08028 Barcelona Spain Fax 34 93 402 45 20 Tel 34 93 403 45 00 E-mail pedromarrero@ Received 4 September 2008 revised 15 October 2008 accepted 31 October 2008 doi Human carnitine palmitoyltransferase 1B CPT1B is a highly malonyl-CoA-sensitive enzyme IC50 pM and has a positive determinant residues 18-28 of malonyl-CoA inhibition. By contrast rat carnitine palmitoyltransferase 1A is less sensitive to malonyl-CoA inhibition IC50 IM and has both a positive residues 1-18 and a negative residues 18-28 determinant of its inhibition. Interestingly pig CPT1B shows a low degree of malonyl-CoA sensitivity IC50 pM . Here we examined whether any additional molecular determinants affect malo-nyl-CoA inhibition of CPT1B. We show that the malonyl-CoA sensitivity of CPT1B is determined by the length either 50 or 128 residues of the N-terminal region constructed by recombining pig and human enzymes. We also show that the N-terminal region of pig CPT1B carries a single positive determinant of malonyl-CoA sensitivity but that this is located between residues 1 and 18 of the N-terminal segment. Importantly we found a single amino acid variation D17E relevant to malonyl-CoA sensitivity. Thus Asp17 is specifically involved under certain assay conditions in the high malonyl-CoA sensitivity of the human enzyme whereas the