N-acetylated amino acids

In the LC-MS data we’ve gathered over the past year, there is frequently strong peaks for N-acetylated amino acids, and there is clear incorporation of labeled acetate from U-13C-glucose, showing that these species are endogenously synthesized (over 48h incubations, mostly). It’s intriguing because, as far as I can tell, there is no known mechanism for N-acetylation of free amino acids in humans.

What about protein acetylation? Free acetylated amino acids could be a product of breakdown of acetylated residues in protein, but the well known protein acetylations (lysine, for example) happens on amino acid side chains, not on the amine (alpha) nitrogen which is part of the peptide bond.

But it turns out that proteins are in fact often acetylated on their N- terminal amino acid. This phenomenon was discovered 40 years ago, but what the heck it’s good for is still being debated. So maybe this explains the N-acetyl amino acids we often see.  Or maybe it’s something different entirely …


2 thoughts on “N-acetylated amino acids”

  1. Since that is acetilated from glucose, it looks as it happens on purpose, not b y chance, right? So there have to be some enzymes for it. And there are too many of them to be just degradation product of N-acetilated proteins. Do they play some biological role by themself?

  2. Certainly these are catalyzed reactions, and the enzymes (N-terminal acetyltransferases, NATs) have been identified; see the PLoS article linked to above. I don’t know if there is acetylation also of free amino acids, and if so what role that would serve.

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