Lipoxygenase isoenzymes from Solanum tuberosum

Two lipoxygenase isoenzymes were separated from potato tubers (Solanum tuberosum). Experiments with chemical modifications showed that tryptophan is essential for enzyme activity and that one or more tryosine residues was involved. On the other hand, no lysine or sulfhydryl groups were necessary. Both enzymes had an optimum pH of 5·5. They were not affected by calcium ions but were inhibited by cysteine.