Physiology, catalase function

The facility of metal complex formation is underscored by the fact that most porphyrin systems with any type of physiological function occur as metal complexes (e.g. Fe in hemoglobins, myoglobins, cytochromes, catalases and peroxidases Mg in chlorophylls and bacteriochlorophylls Co in vitamin B12). 

Oshino, N. and Chance, B. (1977) Properties of glutathione release observed during reduction of organic hydroperoxide, demethylation of aminopyrine and oxidation of some substances in perfused rat liver, and their implications for the physiological function of catalase. Biochem. J. 162 509-525. 

As discussed in the first section of this chapter, the P450 cytochromes, NOS, HOs, and cytochrome oxidases are all heme enzymes which are able to activate molecular oxygen. Related heme enzymes, such as the peroxidases and catalases, work with partially reduced dioxygen species. It has always been intriguing that each of these enzymes uses the same cofactor, heme or Fe-protoporphyrin IX, but performs a distinct physiological function. 

Sumner in a recent paper (300) criticized the term hydroperoxidases on the grounds that there are differences in molecular weight and physiological function between catalase and peroxidase. 

The observations of Bass, et al. (11), that preparations of beef and horse liver catalase could supply V factor activity for H. influenzae,-were interpreted by them as real, and not due to the presence of phospho-pyridine nucleotides as impurity, mainly on the results of comparative heat stability experiments. This interpretation is not yet acceptable in view of Schlenk and Gingrich s findings (327, 103b) that nicotinamide nucleoside has high Y factor activity. A physiological function of catalase activity as replacing V factor activity was excluded by showing that destruction of catalase activity did not destroy the apparent V factor activity of the preparations. A cautious attitude to these observations is necessary until more is known about the exact composition of the catalase preparations used. 

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