Acetylation



Acetylation (or in organic compound. Deacetylation is the removal of the acetyl group.

Moreover, it is that process of introducing an acetyl group (resulting in an acetoxy group) into a compound, specifically, the substitution of an acetyl group for an active hydrogen atom. A reaction involving the replacement of the hydrogen atom of a hydroxyl group with an acetyl group (CH3 CO) yields a specific Aspirin.

Acetylation of proteins

In biology, i.e. in living cells, acetylation occurs as a co-translational and histones and tubulins.

N-alpha-terminal Acetylation

Acetylation of the N-terminal alpha-amine of proteins is a widespread modification in eukaryotes. 40-50% of yeast proteins, and 80-90% of human proteins are modfied in this manner, and the pattern of modification is found to be conserved throughout evolution. The modification is performed by N-alpha-acetyltransferases (NATs), a sub-family of the GNAT superfamily of acetyltransferases, which also include histone acetyl transferases. The GNATs transfer the acetylgroup from acetyl-coenzyme A to the amine group. The NATs have been most extensively studied in yeast. Here three NAT complexes, NatA/B/C, have been found to perform most N-alpha-terminal acetylations. They have sequence specificity for their substrates, and it is believed that they are associated with the ribosome, where they acetylate nascent polypeptides co-translationally.

In humans, only one NAT complex , the human NatA, has been identified and characterized. Subunits of the human NatA complex have been coupled to cancer-related processes such as hypoxia-response and the beta-catenin pathway. It has been found to be over-expressed in papillary thyroid carcinoma and neuroblastoma.

Despite being such a conserved and widespread modification, little is known about the biological role of N-alpha-terminal acetylation. Proteins such as actin and tropomyosin has been found to be dependent of NatB acetylation to form proper actin filaments. This is yet only an example of the potential importance of this modification.

Histone Acetylation and Deacetylation

In gene regulation.

Typically, these reactions are catalyzed by histone deacetylase" (HDAc) activity.

Tubulin Acetylation and Deacetylation

Tubulin Acetylation and Deacetylation system is well worked out in Chlamydomonas. A Tubulin acetyltransferase located in the axoneme acetylates a specific lysine residue in the α-tubulin subunit in assembled microtubule. Once disassembled, this acetylation can be removed by another specific deacetylase which is cytosolic. Thus the axonemal microtubules (long half life) carry this signature acetylation absent from cytosolic microtubules (short half life).

See also

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