Catalase Enzyme

A Glimpse into the Catalase Enzyme BLC... 
(Bovine Liver Catalase)

     Living organisms rely on oxygen to power our cells, but living with oxygen is dangerous. Oxygen is a reactive molecule that can cause serious problems if not carefully controlled. Oxygen can easily convert into other reactive compounds, making it very dangerous. Inside our cells, carrier molecules move electrons from site to site. If oxygen runs into one of these carrier molecules, the electrons could transfer to it. This can convert oxygen into a dangerous compound, such as hydrogen peroxide, which can attack sulfur atoms and metal ions in proteins. The free iron ions in the cell occasionally convert hydrogen peroxide into hydroxyl radicals. These deadly molecules then attack and mutate DNA. A controversial theory is, this type of oxidative damage accumulates over the years of our life, causing us to age. 

     To fight these dangerous side-effects of living with oxygen, our cells make a variety of antioxidant enzymes. One key part in this is, catalase, which converts hydrogen peroxide into water and oxygen gas. These catalase molecules patrol the cell, and counteract the steady production of hydrogen peroxide, keep the levels in our bodies safe. 

     Catalases are some of the most efficient enzymes found in cells. Each catalase molecule can decompose millions of hydrogen peroxide molecules every second. Our own catalases use an iron ion to assist in this speedy reaction. The enzyme is compose of four identical subunits, each with its own active site buried deep inside. Iron ions are gripped at the center of a disk-shaped heme group. Catalase, are unusually stable enzymes, with four chains interweaving, and locking the entire complex into the proper shape. 

     Bovine liver catalase was one of the first enzymes to be isolated to a high state of purity and the first iron-containing enzyme to be isolated. The reaction mechanism was initially proposed to be a free radical mechanism by Oppenheimer and Stern in 1939. Throughout the next few decades, catalysis was determined to occur at the iron atom of the porphyrin . A more convenient method of preparing crystalline catalase from bovine liver was developed in 1952 by Tauber and Petit, and X-ray structure studies of the heme region of myoglobin examined the heme-containing active site.

     The reaction of catalase occurs in two steps. A molecule of hydrogen peroxide oxidizes the heme to an oxyferryl species. A porphyrin cation radical is generated when one oxidation equivalent is removed from iron and one from the poryphyrin ring. A second hydrogen peroxide molecule acts as a reducing agent to regenerate the resting state enzyme, producing a molecule of oxygen and water. Recently, catalase has been investigated as a possible agent to support methods of intracellular drug delivery. Catalase has also been incorporated into an assay for cholesterol quantification and a biosensor for alcohol determination    

     Bovine liver catalase has a molecular weight of 240kDA and a chemical formula C₂₁ H₃₀ N₇ O₁₇ P₃ . The Active site is Histidine (H74) and Asparagine (N147). Activators are Sodium Arsenate and a reaction catalyze H2O2 + H2O2 => H2O + O2

     In nature, somethings seem very simple to the naked eye. Although, when dealing with the chemical structure of things, that naked eye can not see how complex things are inside the body. Things that are as simple as living with oxygen can be as complex as the catalase enzyme that is used to support the oxygen within our bodies. 

Sources:

http://www.worthington-biochem.com/ctl/default.html

http://www.callutheran.edu/BioDev/omm/catalase/frames/cattx.htm#Topic1

http://0-www.jstor.org.library.acaweb.org/stable/10422

http://www.rcsb.org/pdb/explore/explore.do?structureId=1qqw

http://proteopedia.org/wiki/index.php/1qqw