Sandbox Reserved 1096: Difference between revisions
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==='''Catalysis of deimination'''=== | ==='''Catalysis of deimination'''=== | ||
As mentioned before, PAD2 is a calcium-dependent enzyme which catalyzes the deimination. This reaction occurs only if calcium ions bind to specific sites of PAD2 but they don’t directly participate in catalysis : they are cofactors only. Once bonds with calcium have been formed, a '''''catalytic cysteine residue in position 647''''' in the peptidic chain changes its position to realize a [https://en.wikipedia.org/wiki/Nucleophilic_substitution nucleophilic attack] on guanidium groups of arginine residues. | |||
These arginine residues that are substrates in this reaction can bind to PAD2 because calcium binding engenders a move out of the active site for an arginin in position 347 and a move in for a tryptophan in position 348, in order to form a pocket for the substrate<ref name="ART1" />. | |||
== Citrullination of Arginine residues == | == Citrullination of Arginine residues == | ||
In humans, PAD2 is involved in a type of post-translational modification called citrullination. Indeed, this calcium-dependent enzyme catalyzes a deimination reaction : PAD2 uses one molecule of water to replace the terminal nitrogen of Arginine by an oxygen and a ketone group is formed in place of a ketimine one <ref name="ART1" />. | In humans, PAD2 is involved in a type of post-translational modification called citrullination. Indeed, this calcium-dependent enzyme catalyzes a deimination reaction : PAD2 uses one molecule of water to replace the terminal nitrogen of Arginine by an oxygen and a ketone group is formed in place of a ketimine one <ref name="ART1" />. | ||
The transformation of arginyl residues ([https://fr.wikipedia.org/wiki/Arginine Arginine]), which are positively charged at a neutral pH, into citrullyl residues, which are neutral, leads to the '''''modification of the global charge''''' of the targeted protein. These residue modifications are the result of hydrolysation of guanidinium groups in side chains | The transformation of arginyl residues ([https://fr.wikipedia.org/wiki/Arginine Arginine]), which are positively charged at a neutral pH, into citrullyl residues, which are neutral, leads to the '''''modification of the global charge''''' of the targeted protein. These residue modifications are the result of hydrolysation of guanidinium groups in side chains whose catalysis has been explained previously. As a result, the deimination reaction catalyzed by PAD2 may produce '''''important conformational changes''''' in proteins by increasing the hydrophobicity. | ||
== Role in Human Health == | == Role in Human Health == | ||
