SUMMARY The oxygen monitor was used in determining the linoleic acid oxidizing capacity of various plant tissues. Egg plant, potato, legume seeds, cauliflower and avocado contained considerable activity. The effects of nonionic detergents point to the presence of three types of lipoxygenase in the tissues tested. These are: (1) not affected by the detergent; (2) inhibited; and (3) either solubilized or stimulated by the detergent. Some tissues had considerable antioxidant activity as measured by their effect on commercial soybean lipoxygenase. These results lead to the conclusion that a low lipoxygenase activity may be due to the presence of antioxidants and definite conclusions cannot be drawn unless the enzyme is purified.
Purification of pronase by ion-exchange chromatography gave four proteolytically active fractions. Fraction A(2) contained an endopeptidase that attacks poly l-valine. Fraction B contained an endopeptidase, an aminopeptidase and carboxypeptidases. The activities against hippuryl-l-arginine and hippuryl-l-phenylalanine could be inhibited to a considerable extent by di-isopropyl phosphorofluoridate and by EDTA. Fraction C contained an endopeptidase resembling bovine trypsin. The pure enzyme was completely inactivated by di-isopropyl phosphorofluoridate and pancreatic trypsin inhibitor and to about 90% by other naturally occurring trypsin inhibitors. Fraction D contained an apparently homogeneous endopeptidase, inhibited by diisopropyl phosphorofluoridate, that adsorbed to and hydrolysed elastin. The activity of all these fractions was tested qualitatively against a wide range of small peptides and synthetic substrates.
Egg plant lipoxygenase EC 1.13.1.13 when purified on Ecteola cellulose was resolved into two active fractions with most of the activity in the first fraction (A). This fraction when further purified on Sephadex G200‐120 had 20 times the specific activity of the crude material. It proved to be a single substance by electrophoresis and immunological technique. The pH optimum was 6.5. Its activity was specific for thecis,cis‐1,4 pentadiene structure. There was no inhibition by cyanide, azide, EDTA or fluoride. Nordihydroguaretic acid, on the other hand, exhibited strong inhibition at 3 × 10−3M concentration. The specific antibody caused 50% inhibition.
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