Lipoxidases

Smith et al. (1978) have described a procedure for the GLC determination of cis and trans isomers of unsaturated fatty acids in butter after fractionation of the saturated, monoenoic, dienoic, and polyenoic fatty acid methyl esters by argentation TLC. Total trans acids were much higher, as measured by infrared spectrophotometry than by GLC, probably because some of the acids could have two or more of the trans bonds designated as isolated by infrared spectrophotometry. Enzymatic evaluation of methylene-interrupted cis, cis double bonds by lipoxidase resulted in lower values than those obtained by GLC. The authors mention that the lipoxidase method is difficult, requiring considerable skill, and suggest that their method is suitable for the determination of the principal fatty acids in complex food lipids such as bovine milk fat. 

The antagonisms that exist between unsaturated fatty acids, and carotene and vitamin E are cnmplicaled and largely undefined. Linoleic acid acts as an antiviiamin to d/- -locopherol (vitamin E) by reducing availability through direct intestinal destruction. Various lipoxidases destroy carotenes and vitamin A. 

Surrey, K. 1964. Spectrophotometric method for determination of lipoxidase activity. Plant Physiol. 39 65-70. 

In addition to those reactions described above, it appears that chlorophyll can be degraded by yet another pathway. Chichester and McFeeters (1971) reported on chlorophyll degradation in frozen beans, which they related to fat peroxidation. In this reaction, lipoxidase may play a role, and no... 

This enzyme, formerly named lipoxidase, is present in plants and catalyzes the oxidation of unsaturated fats. The major source of... 

Predict the diffusivity of lipoxidase at 293 K in water as a dilute solution and compare with the experimental data in Table 6.4. 

We have attempted to employ microwave heating to inactivate the objectionable trypsin inhibitors and lipoxidase systems. 

It will be noted that the two proteins, trypsin inhibitor and lipoxidase, are apparently influenced differently by the microwave treatment. While microwave heating is more effective than hot water in destroying trypsin inhibitors (Table II) the reverse is true for lipoxidases(Table III). 

In 1940 J. B. Sumner and R. J. Sumner (10) and Tauber (11) recognized that the fat oxidase or lipoxidase and carotene oxidase were identical. From their work it became clear that the enzyme catalyzed the peroxidation of unsaturated fats as the primary reaction and that carotene destruction occurred only during the active enzymatic attack on the fat in a coupled reaction. 

There are two types of lipid peroxidation chemical (nonenzymic) peroxidation and enzyme-catalyzed peroxidation. The nonenzymic peroxidation has been described above. In the enzyme-catalyzed peroxidation, lipoxidases (or lipoxygenases), which are present in both plants and animals, catalyzed the following reaction ... 

Concerning lipolysis in fish muscle, an important advance has been made by Khan (1952). It was shown a long time ago (Banks, 1938) that a lipoxidase system contributing notably to the development of rancidity is localized in the lateral brown band of fatty fishes. This enzyme is very detrimental for the conservation of fish (Reay and Shewan, 1949 Dyer, 1951). Preparations over two thousand times as active as the raw material have been obtained (Khan, 1952), which require for activity some iron-containing, heat-stable activator. No way has yet been found of overcoming the detrimental action of this enzyme. 

---