Apparent Antibacterial Activity of Catalase: Role of Lipid Hydroperoxide Contamination

Escherichia coli was killed by catalase in dose-, time-, and pH-dependent manners. Dialyzed catalase had bactericidal activity, but enzyme which had been heat-denatured or inactivated by pretreatment with 3-aminotriazole plus hydrogen peroxide did not. Cytochrome c and hemoglobin also had bactericidal activity. Thiobarbituric acid-reactive substances were detected in commercial hemoproteins except for horseradish peroxidase and the relationship between the contents of these substances and bactericidal activity was demonstrated. Without the addition of hydroperoxide, hemoproteins except for horseradish peroxidase initiated the oxidation of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfo-nic acid) (ABTS) and catalase caused the peroxidation of linoleic acid. The pH patterns of bactericidal activity, lipid peroxidation, and the oxidation of ABTS were similar. The results indicate that hemoprotein preparations are contaminated with lipid hydroperox-ides and it is the decomposition of these contaminants catalyzed by the hemoprotein into alkoxyl/peroxyl radicals that causes bacterial killing.