title: Effects of octylglucoside and triton X-100 on the kinetics and specificity of carnitine palmitoyltransferase.
abstract: The effects of octylglucoside on the substrate specificity, kinetics and aggregation state of purified carnitine palmitoyltransferase (CPT) from beef heart mitochondria were investigated and compared to the effects of Triton X-100. Conditions in which CPT can be assayed in the absence of micelles and albumin, thereby eliminating miceller effects on the kinetic parameters, are described. When octylglucoside is substituted for Triton X-100, the specificity of CPT in the forward direction shifts towards the long-chain acyl-CoAs, and large changes in the kinetic constants are observed. The K0.5 for L-carnitine varied as much as 50-fold, depending on the acyl-CoA and detergent used. At pH 8.0 and 200 microM palmitoyl-CoA, the K0.5 for L-carnitine is 4.9 mM in 12 mM octylglucoside and 0.2 mM in 0.1% Triton X-100. Octylglucoside enhances the activity of CPT with long-chain acyl-CoA and lowers the K0.5 for these substrates. At pH 6.0, the K0.5 for palmitoyl-CoA is 24.2 microM in 0.1% Triton X-100, in contrast to 3.1 microM in 12 mM octylglucoside. Octylglucoside is a competitive inhibitor of CPT with octanoyl-CoA as substrate with a Ki of 15 mM. Nonlinear kinetics for both acyl-CoAs and L-carnitine are observed when the concentration of octylglucoside is reduced to less than half of its critical micellar concentration (cmc). Gel filtration of CPT in octylglucoside below its cmc gives a single protein peak with a molecular mass of ca. 660,000 daltons.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Biochemistry Department, Michigan State University, East Lansing 48824.
authors: C J
authors: CJ
authors: Fiol
authors: L L
authors: LL
authors: Bieber
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism*; D002417:Cattle; D003902:Detergents / Q000494:pharmacology*; D005960:Glucosides / Q000494:pharmacology*; D006027:Glycosides / Q000494:pharmacology*; D007700:Kinetics; D008823:Micelles; D008970:Molecular Weight; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology*; D013379:Substrate Specificity; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D000214:Acyl Coenzyme A; D003902:Detergents; D005960:Glucosides; D006027:Glycosides; D008823:Micelles; D013501:Surface-Active Agents; C018619:octyl-beta-D-glucoside; D011092:Polyethylene Glycols; D017830:Octoxynol; D000217:Acyltransferases; D002334:Carnitine O-Palmitoyltransferase