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Partially purified lipoxygenase (LOX) extracts were obtained from Fusarium oxysporum, Fusarium proliferalum, Saccharomyces cerevisiae and Chlorella pyrenoidosa by precipitation with ammonium sulfate. The enzymatic extracts from F. oxysporum and S. cerevisiae both exhibited two optimal activities at pH 8.0 and 10.0 while those from F. proliferatum and C. pyrenoidosa showed one optimal pH at 6.0 and 4.5, respectively. The enzymatic extract from F. proliferalum showed the highest LOX activity. The lowest LOX activity was exhibited in the C. pyrenoidosa extract. At pH 8.0, LOX activity from F. oxysporum and S. cerevisiae was inhibited by potassium cyanide (KCN), exhibiting a non-competitive inhibitory effect; however, at pH 10.0, KCN had relatively little effect on enzyme activity. In addition, KCN markedly inhibited LOX activity from C. pyrenoidosa. In contrast, the results showed that the enzymatic activity from F. proliferatum remained relatively stable at KCN concentrations as high as 60 mM. The addition of 5 MM sodium ethylenediaminetetraacetate was found to increase the enzymatic activity from F. oxysporum by 50.3 and 16.6% at pH 9.0 and 10.0, respectively, from F. proliferatum by 50%, and produced a noticeable eight-fold increase in the enzymatic activity from C. pyrenoidosa. Hydroquinone (HQ) resulted in a 2-fold increase in LOX activity from F. proliferalum whereas a competitive inhibitory effect on LOX activity from S. cerevisiae was observed at pH 8.0. The enzymes from the four sources demonstrated an overall preference towards linoleic acid, followed by linolenic acid. In addition, the enzymatic extract from F. proliferatum showed a strong preference towards the glycerol fatty acid esters. Linoleic acid was bioconverted into 9- and 13-hydroperoxides (HPODEs) by all four extracts; in addition, the LOX activity in the F. oxysporum extract produced the 10- and 12-HPODEs from linoleic acid while that of the C. pyrenoidosa extract produced only the 10-HPODE. T

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Lipoxygenase was extracted from Canola seeds (Brassica napus cv, Westar) and partially purified by precipitated with ammonium sulfate at 20-50% of saturation. The optimum pH for the enzyme activity was 7.5 and its K$ sb{ rm m}$ value was 2.0 $ times$ 10$ sp{-4}$ M. The activity of the enzyme extract was considerably greater on linoleic acid than on its ester or on linolenic acid. The effect of cyanide on the enzyme activity was also investigated. / Further purification of the enzyme extract was performed by successive chromatography on ion-exchange and gel filtration, using FPLC system. Four lipoxygenase isozymes (I, IIA, IIB and III) were separated. The homogeneity of each isozyme was demonstrated by the presence of a single protein band on SDS-PAGE gel electophoresis. The molecular weights of isozymes I, IIA, IIB and III were, respectively, 72,000, 106,000, 78,000 and 62,000. The optimum pH for lipoxygenase activity was 6.5 for isozyme I and 6.0 for isozymes IIA, IIB and III.

Thesis (M. S.)--Florida State University, 2006. / Advisor: Betty J. Gaffney, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains viii, 52 pages. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

The biocatalysis of purified soybean lipoxygenase (LOX) (EC 1.13.11.12) using linoleic acid as a substrate model was investigated in selected organic solvent media, including chloroform, dichloromethane, hexane, iso-octane, octane and toluene. The results indicated that there was a 2.6 fold increase in LOX activity in the monophasic iso-octane medium compared to that obtained in the aqueous medium. In addition, the optimum concentration of octane and iso-octane in the biphasic medium containing the organic solvent and Tris-HCl buffer solution, was determined to be 3.5 and 4%, respectively, for LOX activity which resulted in a further increase in LOX activity. The immobilized LOX showed better substrate specificity towards linoleic acid, followed by arachidonic acid. The enzymatically-catalyzed end-products were investigated, and the results indicated that different proportions of the 9- and 13-HPOD isomers were produced by LOX biocatalysis depending on the reaction medium used and the free or immobilized state of the enzyme. (Abstract shortened by UMI.)

Thesis (Ph.D.). / Written for the Dept. of Food Science and Agricultural Chemistry. Title from title page of PDF (viewed 2008/05/12). Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains vii, 90 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 78-88).