Changes in the fluorescence and absorbance of lipoxygenase-1 induced by 13-Ls-hydroperoxylinoleic acid and linoleic acid.

1. The addition of 13-Ls-hydroperoxylinoleic acid to lipoxygenase-1 (linoleate: oxygen oxidoreductase EC 1.13.11.12) from soybeans at pH 9 and 25 degrees C causes a quenching of the fluorescence of the enzyme at 328 nm when exciited at 280 nm and gives rise to an increase of the absorbance of the enzyme in the 300 nm to 450 nm region. 2. In the absence of 02, addition of linoleic acid to enzyme treated with 13-Ls-hydroperoxylinoleic acid, causes an increase of the fluorescence at 328 nm and a decrease of the absorbance in the 300 nm to 450 nm region. 3. The fluorescence changes are suggested to be directly coupled to the absorbance changes via a non-radioactive energy transfer process. 4. It is proposed that the observed fluorescence and absorbance changes are related to changes in the formal change of iron in the protein.