Papel de las actividades superóxido dismutasa y catalasa en la ...

INTRODUCTION
Some catalases have also peroxidase activity and in this case an organic electron
donor, or sometimes an halide ion, is employed in the reduction of hydrogen peroxide
(equation 6).
(6) RH 2 + H 2 O 2 2H 2 O + R
Catalases have been divided into three groups (Loewen, 1997): monofunctional
catalase with heme group (FeCat); bifunctional catalase with heme group (catalaseperoxidase)
and pseudocatalase without heme group (MnCat), referred to as
pseudocatalase because they are not inhibited by the common catalytic inhibitors, azide
and cyanide.
Superoxide dismutase and catalase activities protect the cells also by preventing
the generation of hydroxyl radical (OH·), a more toxic reactive species.
The role of these enzymes can be essential to protect pathogenic bacteria during
respiratory burst after phagocytosis, therefore superoxide dismutase and catalase are
related to virulence mechanisms (Table 5). The ability of many microorganisms to
infect the host depends on their resistance to ROS production by cells, mainly
monocytes, macrophages and polymorphonuclears. Ironically, evolution has selected
organisms that use these cells as targets, so presence of SOD and catalase in bacteria
will contribute to resistance against host and, therefore, infection establishment.
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