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Food Lipids: Chemistry, Nutrition, and Biotechnology

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13<br />

Fatty Acid Oxidation in Plant Tissues<br />

HONG ZHUANG <strong>and</strong> M. MARGARET BARTH<br />

Redi-Cut <strong>Food</strong>s, Inc., Franklin Park, Illinois<br />

DAVID HILDEBRAND<br />

University of Kentucky, Lexington, Kentucky<br />

I. INTRODUCTION<br />

Oxidation of fatty acids in plant tissues is basically the same as that in animal tissues.<br />

In both systems, fatty acid oxidation occurs by at least four separate pathways: �oxidation,<br />

�-oxidation, monoxygenation, <strong>and</strong> lipid peroxidations. �-Oxidation <strong>and</strong><br />

�-oxidation result in the catabolism of fatty acids. Enzymatic lipid peroxidation<br />

generates important biologically active compounds that have roles in cell responses<br />

to injury. Nonenzymatic lipid peroxidation can be involved in the deterioration of<br />

tissues.<br />

There are differences between fatty acid oxidation as it occurs in plants <strong>and</strong> in<br />

animals. For example, �-oxidation is a major source of energy in animal tissues,<br />

while it is not a major metabolic process in the majority of plant tissues, being<br />

involved only in carbon flux from lipid reserves to carbohydrate in lipid-storing<br />

nutrient tissues of seeds during germination. Complete �-oxidation happens only in<br />

mitochondria of animal cells; in plant cells, thus far, it has been demonstrated only<br />

in peroxisomes. �-Oxidation appears to be required for normal function of brain<br />

tissues of animals; presently, however, the importance of �-oxidation is not well<br />

defined in plant tissues. Monoxygenation of fatty acids is a biosynthetic process,<br />

generating hydroxyl <strong>and</strong> oxo derivatives of surface lipid polymers (cutin, suberin)<br />

in plants, whereas it is evidently a part of catabolic processes in animal tissues. In<br />

animal tissues, polyunsaturated fatty acids (PUFAs) are chiefly peroxidized by autoxidation.<br />

However, in plant tissues, lipid peroxidation has been thought to be predominantly<br />

due to enzymatic processes. The lipoxygenase (LOX) pathway is the<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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