Purification and properties of carnitine acetyltransferase from citric acid producing Aspergillus niger.
Carnitine acetyltransferase was purified from the citric acid producing A. niger mycelium with a protein band showing a relative molecular weight of 77,000 and a pH optimum of 7.3. The K(m) values for the purified enzyme for acetyl-CoA and for carnitine were 0.1 mM and 1 mM, respectively. Carnitine acetyltransferase was located both in the mitochondria and in the cytosol. Both mitochondrial and cytosolic enzyme were purified using ammonium sulfate precipitation, Mono Q and Superose 12 separation. Regarding the localization, except for maximum velocity, there were no differences observed in substrate specificity and inhibition. Inhibition of the enzyme with micromolar concentrations of Cu2+ could contribute to a greater citric acid biosynthesis. Carnitine acetyltransferase can be considered as an enzyme necessary for the transport of acetyl groups through mitochondrial membrane in both directions.
Jernejc
K
K
National Institute of Chemistry, Ljubljana, Slovenia.
Legisa
M
M
D001234:Aspergillus niger / Q000201:enzymology / Q000378:metabolism; D002332:Carnitine O-Acetyltransferase / Q000302:isolation & purification* / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology
D019343:Citric Acid; D002332:Carnitine O-Acetyltransferase