Reticulocyte lipoxygenase exhibits both n‐6 and n‐9 activities

Purified reticulocyte lipoxygenase converts arachidonic acid to both 15- and 12-hydroxyperoxyeico-satetraenoic acids. The proportion of the two reaction products does not change during the purification procedure as shown by HPLC analysis. By means of isoelectric focusing it was not possible to separate the n-6 and n-9 activities. Reticulocyte lipoxygenase was completely inactivated by both 5,8,11-eicosatriynoic and 5,8,11,14-eicosatetraynoic acids in contrast to soybean lipoxygenase-1 which was inactivated only by 5,8,11,14-eicosatetraynoic acid. These results indicate that reticulocyte lipoxygenase exhibits both n-6 and n-9 activities. A contamination of the enzyme preparation with other lipoxygenases, e.g., the n-9 lipoxygenase from thrombocytes appears to be excluded.