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In biochemistry, denaturation is a process in which proteins or nucleic acids lose folded structure present in their native state due to various factors, including application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), agitation and radiation, or heat. [3]
In the less extensive technique of equilibrium unfolding, the fractions of folded and unfolded molecules (denoted as and , respectively) are measured as the solution conditions are gradually changed from those favoring the native state to those favoring the unfolded state, e.g., by adding a denaturant such as guanidinium hydrochloride or urea.
Denaturation midpoint of a protein is defined as the temperature (T m) or concentration of denaturant (C m) at which both the folded and unfolded states are equally populated at equilibrium (assuming two-state protein folding). T m is often determined using a thermal shift assay.
The crystal structure of catechol oxidase purified from Ipomoea batatas has been resolved in its active form in both the oxidized Cu(II)-Cu(II) state and the reduced Cu(I)-Cu(I) state. [11] It is a globular, single domain monomeric enzyme that is approximately 55 by 45 by 45 Å in size and ellipsoid in shape.
Polyphenol oxidase is an enzyme found throughout the plant and animal kingdoms, [31] including most fruits and vegetables. [32] PPO has importance to the food industry because it catalyzes enzymatic browning when tissue is damaged from bruising, compression or indentations, making the produce less marketable and causing economic loss.
Cyanobacterial DesA, [19] an enzyme that can introduce a second cis double bond at the delta-12 position of fatty acid bound to membrane glycerolipids. This enzyme is involved in chilling tolerance; the phase transition temperature of lipids of cellular membranes being dependent on the degree of unsaturation of fatty acids of the membrane lipids.
Superoxide is known to denature enzymes, oxidize lipids, and fragment DNA. [21] SODs catalyze the production of O 2 and H 2 O 2 from superoxide (O − 2), which results in less harmful reactants. When acclimating to increased levels of oxidative stress, SOD concentrations typically increase with the degree of stress conditions.
Glutathione reductase (GR) also known as glutathione-disulfide reductase (GSR) is an enzyme that in humans is encoded by the GSR gene.Glutathione reductase (EC 1.8.1.7) catalyzes the reduction of glutathione disulfide to the sulfhydryl form glutathione (), which is a critical molecule in resisting oxidative stress and maintaining the reducing environment of the cell.