| amino acid | <biochemistry> A class of organic molecules that containing an amino group and can combine in linear arrays to form proteins in living organisms. There are twenty common amino acids: alanine, arginine, aspargine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. They are key components in all living things from which proteins are synthesised by formation of peptide bonds during ribosomal translation of messenger RNA. All the amino acids have the L configuration, except glycine which is not optically active. Other amino acids occurring in proteins, such as hydroxyproline in collagen, are formed by post translational enzymatic modification of amino acid residues in polypeptide chains. There are also several important amino acids, such as the neurotransmitter y aminobutyric acid, that have no relation to proteins. Amino acids can now be produced by biotechnology in bulk using fermentation and biotransformation. Acronym: AA (13 Nov 1997) |
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| amino acid activating enzyme | <enzyme> Enzymes catalyzing the formation of a specific aminoacyl-tRNA from an amino acid and adenosine 5'-triphosphate with the concomitant formation of adenosine 5'-monophosphate and pyrophosphate. Synonym: amino acid activating enzyme, aminoacyl-tRNA ligases. (05 Mar 2000) |
| amino acid activation | The first step of protein synthesis, whereby an amino acid reacts with adenosine triphosphate in the presence of aminoacyl RNA synthetase to produce an amino acid adenylate, which provides the energy necessary for the attachment of the amino acid to a specific transfer RNA molecule. (12 Dec 1998) |
| amino acid analysis | Determination and identification of amino acid content of a macromolecule, identification of a specific amino acid in macromolecules, often a mutated protein, identification and quantitation of amino acid content in blood plasma or urine; a key diagnostic aid. (05 Mar 2000) |
| amino acid chloromethyl ketones | <chemical> Inhibitors of serine proteinases and sulfhydryl group-containing enzymes. They act as alkylating agents and are known to interfere in the translation process. Pharmacological action: alkylating agents, protein synthesis inhibitor, serine proteinase inhibitors. (12 Dec 1998) |
| amino acid dehydrogenases | Enzymes catalyzing the oxidative deamination of amino acids to the corresponding oxo (keto) acids; two relatively non-specific varieties exist, l and d, for which l-amino acids and d-amino acids are the respective substrates; the products include NH3 and a reduced hydrogen acceptor (NADH in the l case); amino acid dehydrogenases of greater specificity exist, (e.g., glycine dehydrogenase). Compare: amino acid oxidases. (05 Mar 2000) |
| amino acid isomerases | <enzyme> Enzymes that catalyze either the racemization or epimerization of chiral centres within amino acids or derivatives. Registry number: EC 5.1.1.- (12 Dec 1998) |
| amino acid naphthylamidases | <enzyme> Registry number: EC 3.4.11. (12 Dec 1998) |
| amino acid neurotransmitters | Amino acids released by neurons as intercellular messengers. Among the amino acid neurotransmitters are glutamate (glutamic acid) and gaba which are, respectively, the most common excitatory and inhibitory neurotransmitters in the central nervous system. (12 Dec 1998) |
| amino acid oxidases | Flavoenzymes oxidizing, with O2 and H20, either l-or d-amino acids specifically, to the corresponding 2-keto acids, NH3 and H2O2. Compare: amino acid dehydrogenases, yellow enzyme. (05 Mar 2000) |
| amino acid oxidoreductases | <enzyme> A class of enzymes that catalyze oxidation-reduction reactions of amino acids. Registry number: EC 1.4. (12 Dec 1998) |
| amino acid permease | <enzyme> A widely distributed group of large Integral membrane proteins, required for the entry of amino acids into cells. (18 Nov 1997) |
| amino acid reagent | A reagent used in the identification and quantification of amino acids. (05 Mar 2000) |
| amino acid receptor | <biochemistry> Ligand gated ion channels with specific receptors for amino acid transmitters. An extended protein superfamily that also includes subunits of the nicotinic acetylcholine receptor. (18 Nov 1997) |
| amino acid sequence | The sequence of amino acids as arrayed in chains, sheets, etc., within the protein molecule. This is referred to as the primary structure of proteins. It is of fundamental importance in determining protein conformation. (12 Dec 1998) |