Molecules: 11/2006

amino acids

Essential amino acids in adult humans: lysine, leucine, isoleucine, methionine, phenylalanine, threonine, tryptophan, and valine.
Additional amino acids essential to children: histidine and arginine.

• amino acid chart • alanine • arginine • asparagine • aspartic acid • cysteine • glutamic acid • glutamine • glycine • histidine • isoleucine • leucine • lysine • N-formylmethionine • methionine • phenylalanine • proline • serine • threonine • tryptophan • tyrosine • valine

External links: Alanine Arginine Asparagine Aspartic acid Cysteine Glutamic acid Glutamine Glycine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tryptophan Tyrosine Valine Essential amino acid Protein Peptide Genetic code Isoleucine and valine biosynthesis Leucine biosynthesis

alanine

Non-polar amino acid Ala A RNA code: GCU, GCC, GCA, GCG

arginine

Basic amino acid Arg R RNA code: CGU, CGC, CGA, CGG, AGA, AGG

asparagine

Polar amino acid Asn N RNA code: AAU, AAC

aspartic acid

Acidic amino acid Asp D RNA code: GAU, GAC

cysteine

Polar amino acid Cys C RNA code: UGU, UGC

glutamic acid

Acidic amino acid Glu E RNA code: GAA, GAG

glycine

Non-polar amino acid Gly G RNA code: GGU, GGC, GGA, GGG

glutamine

Polar amino acid Gln Q RNA code: CAA, CAG

Basic amino acid His H RNA code: CAU, CAC

Histidine's imidazole side chain has a hydrogen-bound nitrogen atom that is slighty acidic and another nitrogen that is slightly basic. The almost neutral pKa of histidine ensures that its charge will change in response to relatively small shifts in cellular pH.

Histidine functions as a co-ordinating ligand in metalloproteins, and at the catalytic site of some enzymes. In catalytic triads, the basic nitrogen of histidine extracts a proton from serine, threonine or cysteine, activating the nitrogen as a nucleophile. In a histidine proton shuttle, histidine rapidly shuttles protons by abstracting a proton onto the basic nitrogen to generate a positively-charged intermediate before passing a proton from the acidic nitrogen. Carbonic anhydrases employ the histidine proton shuttle to rapidly shuttle protons away from a zinc-bound water molecule to quickly regenerate the active form of the enzyme.

isoleucine

Non-polar amino acid Ile I RNA code: AUU, AUC, AUA

leucine

Non-polar amino acid Leu L RNA code: UUA, UUG, CUU, CUC, CUA, CUG

lysine

Basic amino acid Lys K RNA code: AAA, AAG

N-formylmethionine

N-Formylmethionine (fMet) is an amino acid that is found in all living cells. It is a derivative of the amino acid methionine, in which a formyl group has been added to methionine's amino group (catalyzed by the enzyme transformylase when Met is attached to tRNA.fMet, but not to tRNA.Met).

N-Formylmethionine plays a crucial role in the protein biosynthesis of bacteria, archaea, mitochondria and chloroplasts. Bacteria utilize N-formylmethionine (f-Met) rather than methionine at the N-terminal of the elongating polypeptide chain.

Compare to methionine.

f-Met amino acid RNA code: AUG tRNA.fMet & tRNA.Met

Polar amino acid Ser S RNA code: UCU, UCC, UCA, UCG, AGU, AGC

Serine is a biosynthetic derivative of glycine, and a biosynthetic precursor of purines and pyrimidines, cysteine, tryptophan, and other metabolites.

Serine is found in the active sites of many enzymes including the serine proteases chymotrypsin and trypsin.

Serine is important in signal transduction because it is phosphorylated by serine/threonine kinases.

Tyrosine is a biosynthetic precursor of the thyroid hormone thyroxine (T4) and triiodothyronine (T3), the pigment melanin, the catecholamine neurotransmitter dopamine and norepinephrine, the neurotransmitter/hormone epinephrine, and in the opium poppy, morphine.