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Biochemistry of the Peroxisome in the Liver Cell
Author(s) -
Sies Helmut
Publication year - 1974
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.197407061
Subject(s) - peroxisome , catalase , biochemistry , metabolism , enzyme , chemistry , hydrogen peroxide , intracellular , biology , gene
The marker enzyme of the peroxisome—a phylogenetically old yet only recently discovered cell organelle—is catalase, a hemoprotein which decomposes hydrogen peroxide catalatically as well as peroxidatically. In the peroxisomes, catalase is associated with H 2 O 2 ‐producing oxidases and other enzymes. Also in parenchymal cells such as liver and kidney cells part of the reduction of oxygen occurs via formation of H 2 O 2 . A central role in peroxisomal H 2 O 2 ‐metabolism is played by the active intermediate, catalase‐Fe 3+ ‐H 2 O 2 , (Compound I), which is distinguished from free catalase by specific absorption bands. Organ photometry on intact hemoglobin‐free perfused rat liver in order to measure Compound I selectively provides a direct insight into the dynamics of the H 2 O 2 metabolism which takes place in the range of nanomolar concentrations. Endogenously, 1g of liver forms approximately 50 nmol of H 2 O 2 per min. The turnover number, which in the steady state is < 10 min −1 in the cell as compared to > 10 8 min −1 for the isolated enzyme with an excess of substrate, can be increased to approximately 10 2 min −1 by intracellular stimulation of the H 2 O 2 production ( e.g. by glycolate or urate). The peroxidatic oxidation of hydrogen donors ( e.g. methanol and ethanol), favored relative to the catalase pathway at low turnover numbers, is of importance in normal metabolism and in pathological conditions.