Catalase and glutathione peroxidase

The red cell contains a battery of cytosolic enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, to dispose of powerful oxidants generated during its metabolism. 

Marklund, S.L., Westman, N.G., Lundgren, E. and Roos, G. (1982). Copper and zincsuperoxide dismutase, manganese-containing superoxide dismutase, catalase, and glutathione peroxidase in normal and neoplastic human cell lines and normal human tissues. Cancer Res. 42, 1955-1961. 

Garlic s proven mechanisms of action include (a) inhibition of platelet function, (b) increased levels of two antioxidant enzymes, catalase and glutathione peroxidase, and (c) inhibition of thiol enzymes such as coenzyme A and HMG coenzyme A reductase. Garlic s anti-hyperlipidemic effects are believed to be in part due to the HMG coenzyme A reductase inhibition since prescription medications for hyperlipidemia have that mechanism of action (statins). It is unknown whether garlic would have the same drug interactions, side effects, and need for precautions as the statins. 

Catalase and glutathione peroxidase provide two important cellular systems for eliminating H202. Catalase, a 56kDa cytosolic hemoprotein homotetramer that can act without a cofactor, although it may bind NAD(P)H, functions as a peroxidase to convert H202 to water. It can be irreversibly inactivated by oxidation and demonstrates decreased activity after ischemia-reperfusion. Catalase is more abundant in astrocytes than in neurons and in white matter than in gray matter, but it can be induced in neurons by neurotrophins. There is substantially less catalase activity in brain than in other tissues, such as liver. 

In contrast, antioxidant enzymes can efficiently counteract all UV-induced ROS (Aguilera et al. 2002). These enzymes are represented by superoxide dismutase (SOD), catalase and glutathione peroxidase as well as those involved in the ascorbate-glutathione cycle, such as ascorbate peroxidase, mono-dehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase. One of the most important classes of antioxidant enzymes is the SOD family, which eliminate noxious superoxide radical anions. Different metalloforms of SOD exist (Fe, Mn, CuZn and Ni), which due to their intracellular localisation protect different cellular proteins (Lesser and Stochaj 1990). 

Cejkova, J., Stipek, S., Crkovska, J., Ardan, T. Changes of superoxide dismutase, catalase and glutathione peroxidase in the corneal epithelium after UVB rays. Histochemical and biochemical study. Histol Histopathol 15(4), 1043-1050... 

Rats, exposed for 7 days to 85% Oj, survived for more than 4 days in 100% Oj, when control rats died within 3 days. They showed a 50% increase of SOD in their lungs. With guinea-pigs, hamsters, and mice there was no increase of pulmonary SOD and no tolerance was developed This increase in pulmonary SOD at 80% O or more was only observed with 10-day old and not with 25-day old rats. Catalase and glutathione peroxidase were increased with both groups There are, however, modifications at the cellular level besides the increase of the enzyme activities. 

The G-6-PD is a large structure with many genetic variants perhaps more than any other human protein (59-62). It is an almost ubiquitous cytosolic enzyme which catalyzes the first step in the hexose monophosphate pathway (62). Its most essential function is to produce the NADPH required to maintain the concentration of reduced glutathione (GSH) in the face of oxidative stress. The GSH together with catalase and glutathione peroxidase represent the defence against hydrogen peroxide, and this is particularly true in red blood cells. 

In STZ-diabetic rat livers, the levels of mRNA of 1-gulonolactone oxidase, catalase, and glutathione peroxidase were decreased at 6 weeks, as well as that of plasma alpha 1 proteinase inhibitor 3.562 AA synthesis enzyme and recycling enzyme mRNAs were also decreased, as was the level of AA itself. It seems that the antioxidative defence system had been severely damaged. 

Intracellular H2O2 is detoxified by both catalase and glutathione peroxidase. Dimethylthiourea (DMTU), a lipophilic, low-molecular-weight compound, can also scavenge intracellular H2O2 and OH [25]. Due to its low reactivity, H2O2 produced intracellularly can also traverse the cell membrane and initiate extracellular radical reactions (Fig. 1). Extracellular H2O2 can be detoxified by catalase added to the perfusion medium. 

Increased oxidative stress is apparently not a factor in WS since cultured cells from WS patients revealed normal levels of the antioxidative enzymes Cu-Zn and Mn superoxide dismutases, catalase, and glutathione peroxidase (M7). In addition, WS patients had normal lipid peroxidation levels. 

M7. Marklund, S, Nordensson, I, and Back, O., Normal CuZn superoxide dismutase, Mn superoxide dismutase, catalase and glutathione peroxidase in Werner s syndrome. J. Gerontol. 36 405 109 (1981). 

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