Pyrrolysine

Pyrrolysine (Pyl) is an amino acid used in the biosynthesis of proteins in some methanogenic archaea and bacteria. It is the 22nd genetically encoded amino acid, and the only one that is encoded by an amber codon (UAG). Pyrrolysine is encoded by the codon UAG, which is normally a stop codon in other organisms.

Structure

Pyrrolysine is a derivative of lysine, with a pyrroline ring attached to the amino acid's side chain. This gives it a larger size and different chemical properties than lysine.

Biosynthesis

The biosynthesis of pyrrolysine involves a series of enzymatic reactions. The first step is the adenylation of lysine by the enzyme PylB. This is followed by the reduction of the adenylated lysine to a dehydroalanine by PylC. The dehydroalanine is then converted to pyrrolysine by PylD.

Function

Pyrrolysine is used in the active site of certain methyltransferase enzymes, where it plays a crucial role in the methylation of amines. These enzymes are involved in the metabolism of methane in methanogenic archaea.

Discovery

Pyrrolysine was discovered in 2002 by a team of researchers led by Joseph A. Krzycki at Ohio State University. It was the first new amino acid to be discovered in 22 years.

See also

• Selenocysteine
• Genetic code
• Protein biosynthesis

   AAs =

Starts =

 Base1 =

 Base2 =

 Base3 =

Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).

Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V)

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