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Two Lipoxygenases from Germinated Barley‐Heat and Kilning Stability
Author(s) -
HUGUES MIREILLE,
BOIVIN PATRICK,
GAUILLARD FRÉDÉRIC,
NICOLAS JACQUES,
THIRY JEANMARC,
RICHARDFORGET FLORENCE
Publication year - 1994
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1994.tb08150.x
Subject(s) - lipoxygenase , isoelectric point , linoleic acid , chemistry , ammonium sulfate precipitation , germination , thermal stability , isoelectric focusing , ionic strength , chromatography , kinetics , ammonium sulfate , biochemistry , enzyme , food science , biology , botany , organic chemistry , fatty acid , aqueous solution , size exclusion chromatography , physics , quantum mechanics
Using ammonium sulfate precipitation followed by hydrophobic and ion exchange chromatography, two lipoxygenase isoenzymes, LOX 1 and LOX 2, were 18.3‐ and 44.5‐fold purified from germinated barley, with 18 and 24% recovery of activity respectively. LOX 1 and LOX 2 were characterized by isoelectric points 4.9 and 6.4, and molecular weights of 90 kd and 110 kd, respectively. Apparent Km values for linoleic acid were 0.06 mM for LOX 1 and 0.18 mM for LOX 2. LOX 1 converted linoleic acid to 9 and 13 hydroperoxides at about 4:1, whereas the 13 hydroperoxide was the major product formed by LOX 2 (ratio 3:7). For both isoforms, thermal inactivation data indicated first order kinetics with activation energies influenced by ionic strength and pH. Isoenzymes composition was analyzed for three kilning schemes: the 1:3 ratio between LOX 1 and LOX 2 observed in germinated barley increased during the course of kilning.