Biomedical Engineering Reference
In-Depth Information
FIGURE 7.3 Role of catalase in the metabolism of MeOH and FA: perox-
idative activity. Using hydrogen peroxide (H
2
O
2
) as a cofactor, rodent catalase
peroxidatively oxidizes (a) MeOH (CH
3
OH) into formaldehyde (CH
2
O) and
(b) FA (HCOOH) into carbon dioxide and water.
Peroxidative Role In the presence of hydrogen peroxide (H
2
O
2
) and a
hydrogen donor such as an alcohol, the Compound I state of catalase
oxidizes the alcohol to its aldehyde, in the process reducing catalase
back to its resting state (Figure 7.3). In rodents, MeOH is metabolized
by the peroxidative activity of catalase as opposed to ADH1, forming
the toxic formaldehyde metabolite (Karinje and Ogata, 1990; Bradford
et al., 1993). Conversely, humans and non-human primates do not
metabolize MeOH using catalase (Mannering et al., 1969), likely
because of low levels of endogenous H
2
O
2
(Oshino et al., 1975). In
rodents, catalase is also responsible for the peroxidative oxidation of FA
to carbon dioxide and water (Smith and Taylor, 1982; Von Burg, 1994)
(Figure 7.3)—a process that does not occur in humans.
In rodent embryos, peroxidative catalase activity increases with
gestational age, and comparatively, the mouse embryo has consistently
higher specific catalase activity than the rat embryo (Harris et al., 2003)
(Table 7.5). The peroxidative activity of catalase follows Michaelis-
Menten kinetics, where rat catalase demonstrates an affinity for MeOH
of
1.5mM (Perkins et al., 1995).
Antioxidative Role In all species, catalase acts as an antioxidant by
scavenging H
2
O
2
(Figure 7.4) (Halliwell and Gutteridge, 2007; Wells
et al., 2009b). Similar to its peroxidative activity, antioxidative catalase
activity increases throughout gestation and into adulthood in both
humans and rodents, where mouse embryonic catalase activity is
approximately 4% of adult activity (Table 7.6) (Winn and Wells,
1999; Abramov and Wells, 2011). Furthermore, substantial species
differences in antioxidative catalase activity have been documented
(Reddy et al., 1984; Sweeting and Wells, 2010). Unlike the peroxidative
