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Catalase has one of the highest turnover numbers of all enzymes; one catalase molecule can convert millions of hydrogen peroxide molecules to water and oxygen each second. [ 6 ] Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long. [ 7 ]
An enzyme is a substance that acts as a catalyst in living organisms which helps to speed up chemical reactions. [12] Carbonic anhydrase is one important enzyme that is found in red blood cells, gastric mucosa, pancreatic cells, and even renal tubules. It was discovered in the year 1932 and it has been categorized into three general classes. [13]
Enzymes act on small molecules called substrates, which an enzyme converts into products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. The study of how fast an enzyme can transform a substrate into a product is called enzyme kinetics.
As shown on the right, enzymes with a substituted-enzyme mechanism can exist in two states, E and a chemically modified form of the enzyme E*; this modified enzyme is known as an intermediate. In such mechanisms, substrate A binds, changes the enzyme to E* by, for example, transferring a chemical group to the active site, and is then released.
The soluble [NiFe] hydrogenase from Ralstonia eutropha H16 is a promising candidate enzyme for H 2-based biofuel application as it favours H 2 oxidation and is relatively oxygen-tolerant. It can be produced on heterotrophic growth media [ 8 ] and purified via anion exchange and size exclusion chromatography matrices. [ 9 ]
Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the energy-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants , algae , and cyanobacteria .
Nitrification is important in agricultural systems, where fertilizer is often applied as ammonia. Conversion of this ammonia to nitrate increases nitrogen leaching because nitrate is more water-soluble than ammonia. Nitrification also plays an important role in the removal of nitrogen from municipal wastewater.
After separation from glucose, galactose travels to the liver for conversion to glucose. [12] Galactokinase uses one molecule of ATP to phosphorylate galactose. [ 2 ] The phosphorylated galactose is then converted to glucose-1-phosphate, and then eventually glucose-6-phosphate, which can be broken down in glycolysis.