Increased Transglutaminase Activity in Elicited and Activated Macrophages: Relationship to Production of Superoxide Anion

To evaluate whether transglutaminase (TG) might be involved in production of oxygen metabolites, TG activity was measured in resident, in activated, and in elicited murine peritoneal macrophages. These various types of macrophages show a wide diversity in their ability to generate oxygen metabolites. Like other transglutaminases, the macrophage enzyme was found to be a calcium‐dependent enzyme that was stabilized by dithiothreitol and inhibited by dansylcadav‐ erine. The TG activity was approximately six‐times higher in lysates of LPS‐ elicited macrophages compared with lysates of resident macrophages; this paralleled the six‐fold increase in phorbol myristate acetate‐stimulated release of superoxide anion (O 2 ). From mixing experiments, the difference in TG activity was not due to an endogenous cellular inhibitor in the resident cells. The apparent K m of TG for putrescine was similar in lysates of resident and LPS‐elicited macrophages, but the V max was significantly greater in lysates of LPS‐elicited cells. Macrophages obtained from mice injected with either viable bacillus Calmette‐Guérin, muramyl dipeptide, or killed Corynebacterium parvum released three‐ to six‐ times more O 2 than did resident macrophages. The TG activity in these macrophages was also two‐ to six‐ times higher than in resident cells. However, macrophages that were primed by exposure to LPS in vitro exhibited increased production of O 2 but no increase in TG activity. We conclude that enhanced TG activity is not a prerequisite for the enhanced O 2 production observed in activated macrophages.