title: Partial purification and kinetic characterization of a carotenoid cleavage enzyme from quince fruit (Cydonia oblonga).
abstract: For the first time, a cytosolic carotenoid cleavage enzyme isolated from quince (Cydonia oblonga) fruit is described. The enzyme was partially purified by using centrifugation, acetone precipitation, ultrafiltration (300 kD, 50 kD), isoelectric focusing (pH 3-10), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (7.5%). In this way, an enzymatically active protein fraction was obtained that contained three similar proteins, all exhibiting molecular weights in the range of 20 kD. Using beta-carotene as substrate, the enzyme activity was detected spectrophotometrically at a wavelength of 505 nm. The time constant of the reaction was 8.2 min, the Michaelis constant (K(m)) was 11.0 micromol x L(-1), and the maximum velocity (v(max)) was 0.083 micromol x L(-1) x min(-1) x mg(protein)(-1). The optimum temperature was above 50 degrees C.
authors.affiliation: Institute of Food Chemistry, TU Braunschweig, Schleinitzstrasse 20, DE 38106 Braunschweig, Germany. p.fleischmann@tu-bs.de
authors.forename: Peter
authors.initials: P
authors.lastname: Fleischmann
authors.forename: Kerstin
authors.initials: K
authors.lastname: Studer
authors.forename: Peter
authors.initials: P
authors.lastname: Winterhalter
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D005638:Fruit / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D007700:Kinetics; D010088:Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D013053:Spectrophotometry; D013696:Temperature; D019207:beta Carotene / Q000378:metabolism
chemical_list: D019207:beta Carotene; D002338:Carotenoids; D010088:Oxidoreductases