Purification and some properties of catalase from wheat germ (Triticum aestivum L.).
Two isoforms of catalase, CAT-1 and CAT-2, were purified from wheat germ after extraction, ammonium sulfate precipitations, hydrophobic chromatography, and two ionic-exchange chromatographies. The global yields and the purification factors were close to 3% and 50 for CAT-1 and close to 6% and 100 for CAT-2. Both isoforms exhibit an optimum activity at pH 7. When pH was decreased from 7 to 5.6, CAT-1 showed a decreasing affinity for its substrate, whereas the opposite was found for CAT-2. Both isoforms were irreversibly denaturated when exposed to acidic pH, CAT-1 being more sensitive than CAT-2. Conversely, CAT-2 appeared to be more sensitive to inhibitors. The rate as well as the extent of denaturation during incubation with 3-amino-1,2,4-triazole (AT) were higher with CAT-2 than with CAT-1. Guaiacol is a competitive inhibitor more potent with respect to CAT-2. The difference in affinity for hydrogen peroxide as well as the poor stability of CAT-1 in acidic medium suggests that this isoform could be less effective during dough mixing.
Garcia
R
R
Chaire de Biochimie Industrielle et Agro-alimentaire, Conservatoire National des Arts et Métiers, 292 Rue Saint-Martin, 75141 Paris Cedex 03, France.
Kaid
N
N
Vignaud
C
C
Nicolas
J
J
D002374:Catalase / Q000302:isolation & purification* / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008084:Lipoxygenase / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D012639:Seeds / Q000201:enzymology; D014908:Triticum / Q000201:enzymology*
D007527:Isoenzymes; D010544:Peroxidases; D002374:Catalase; D008084:Lipoxygenase