Some properties of gingival 12-lipoxygenase activity in human and dog

Arachidonate lipoxygenase activity in gingival tissue was investigated and compared with that of enzymes from other sources. 12-lipoxygenase activity was detected in homogenates of human and dog gingiva after 2 min incubation with exogenous arachidonic acid. 12-HETE was the major metabolite in both species. The 12-lipoxygenase activity in homogenates of human gingiva and in platelets was inhibited by EDTA; it recovered after the addition of a divalent cation such as Ca2+. Its activity in dog gingiva and platelets was not affected by the chelator. Gingival 12-lipoxygenase, unlike platelet 12-lipoxygenase, was inhibited by AA861, a possible 5-lipoxygenase inhibitor. These findings suggest that gingival tissue has high levels of 12-lipoxygenase activity, but the enzyme in human gingiva differs from that in the dog in its dependency upon divalent cations, and gingival 12-lipoxygenase differs from the same enzyme in platelets in its sensitivity to an inhibitor.