| amino acid substitution | The naturally occurring or experimentally induced replacement of one or more amino acids in a protein with another. If a functionally equivalent amino acid is substituted, the protein may retain wild-type activity. Substitution may also diminish or eliminate protein function. Experimentally induced substitution is often used to study enzyme activities and binding site properties. (12 Dec 1998) |
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| amino acid transmitter | <biochemistry> Amino acids released as neurotransmitter substances from nerve terminals and acting on postsynaptic receptors for example _ aminobutyric acid (GABA) and glycine that are fast inhibitory transmitters in the mammalian central nervous system. Glutamate and aspartate mediate fast excitatory transmission. Strychnine (for glycine) and bicuculline for GABA) are blocking agents for amino acid action. (18 Nov 1997) |
| aminocaproic acid | <chemistry> A group of compounds that are derivatives of aminohexanoic acids. <haematology> An antifibrinolytic agent, used to prevent bleeding in haemophilia, and after heart and prostate surgery when plasminogen or urokinase may be activated. (05 Mar 2000) |
| aminocarboxylic 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) |
| aminocitric acid | HOOCCH(NH3+)C(COOH)(OH)CH2CO; OH;found in acid hydrolysates of ribonucleoprotein in human spleen. (05 Mar 2000) |
| aminoethanoic acid | <amino acid, physiology> The simplest amino acid. It is a common residue in proteins, especially collagen and elastin and is not optically active. It is also a major inhibitory neurotransmitter in spinal cord and brainstem of vertebrate central nervous system. (18 Nov 1997) |
| aminoethylphosphonic acid | <chemical> (2-aminoethyl)-phosphonic acid. An organophosphorus compound isolated from human and animal tissues. Chemical name: Phosphonic acid, (2-aminoethyl)- (12 Dec 1998) |
| aminolevulinic acid | <chemical> Chemical name: Pentanoic acid, 5-amino-4-oxo- (12 Dec 1998) |
| aminooxyacetic acid | <chemical> (aminooxy)acetic acid. A compound that inhibits aminobutyrate aminotransferase activity in vivo, thereby raising the level of gamma-aminobutyric acid in tissues. Pharmacological action: enzyme inhibitors, gaba agents. Chemical name: Acetic acid, (aminooxy)- (12 Dec 1998) |
| aminopropionic acid | <amino acid> Alanine is a nonessential amino acid that can be manufactured by the body from other sources as needed. Alanine is one of the simplest of the amino acids and is involved in the energy-producing breakdown of glucose. In conditions of sudden anaerobic energy need, when muscle proteins are broken down for energy, alanine acts as a carrier molecule to take the nitrogen-containing amino group to the liver to be changed to the less toxic urea, thus preventing buildup of toxic products in the muscle cells when extra energy is needed. Because the body easily constructs alanine from other sources, no deficiency state is known. Alanine is found in a wide variety of foods, but is particularly concentrated in meats. (22 May 1997) |
| anisic acid | A crystalline volatile acid obtained from anise; its compounds are the antiseptic anisates. Synonym: 4-methoxybenzoic acid. (05 Mar 2000) |
| anthranilic acid | One of the products of tryptophan catabolism. Synonym: o-aminobenzoic acid. (05 Mar 2000) |
| apurinic acid | <chemical> Hydrolysate of DNA in which purine bases have been removed. Chemical name: Apurinic acid (12 Dec 1998) |
| apyrimidinic acid | DNA from which the pyrimidine bases have been removed by chemical treatment (e.g., exposure to hydrazine). (05 Mar 2000) |
| arabic acid | 1. <chemistry> A carbohydrate, isomeric with cane sugar, contained in gum arabic, from which it is extracted as a white, amorphous substance. 2. Mucilage, especially that made of gum arabic. Source: Websters Dictionary (01 Mar 1998) |