Anthrax toxin is composed of a cell-binding protein, known as protective antigen (PA), and two enzyme components, called edema factor (EF) and lethal factor (LF). These three protein components act together to impart their physiological effects. Anthrax lethal factor endopeptidase that catalyzes the hydrolysis of mitogen-activated protein kinase kinases, is a component of the lethal factor produced by the bacterium Bacillus anthracis.