| glycine synthase | A complex of several proteins that catalyze the reversible reaction of glycine with tetrahydrofolate to produce CO2, NH3, and N5,N10-methylenetetrahydrofolate; a deficiency of this enzyme (or one of its subunits) will result in nonketotic hyperglycinaemia. Synonym: glycine synthase. (05 Mar 2000) |
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| glycine transamidinase | <enzyme> An enzyme catalyzing the transfer of an amidine group from l-arginine to glycine, forming guanidinoacetate and l-ornithine; an important reaction in creatine synthesis; it can also act on canavanine. Synonym: glycine transamidinase. (05 Mar 2000) |
| glycine-trna ligase | <enzyme> An enzyme that activates glycine with its specific transfer RNA. Chemical name: Glycine:tRNA(Gly) ligase (AMP-forming) Registry number: EC 6.1.1.14 (12 Dec 1998) |
| adrenergic receptors | Reactive components of effector tissues, most of which are innervated by adrenergic postganglionic fibres of the sympathetic nervous system. Such receptor's can be activated by norepinephrine and/or epinephrine and by various adrenergic drugs; receptor activation results in a change in effector tissue function, such as contraction of arteriolar muscles or relaxation of bronchial muscles; adrenergic receptor's are divided into alpha-receptor's and beta-receptor's, on the basis of their response to various adrenergic activating and blocking agents. Synonym: adrenoceptor, adrenoreceptors. (05 Mar 2000) |
| alpha-adrenergic receptors | Adrenergic receptor's in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as phenoxybenzamine, to block only some adrenergic receptor's and of other agents, such as methoxamine, to activate only the same adrenergic receptor's. Such receptor's are designated as alpha-receptors. Their activation results in physiological responses such as increased peripheral vascular resistance, mydriasis, and contraction of pilomotor muscles. (05 Mar 2000) |
| ANP clearance receptors | Cell surface proteins that bind atrial natriuretic peptide and ANP fragments without initiating biological action. (05 Mar 2000) |
| ANP receptors | Cell surface receptors for atrial natriuretic peptide that have a single transmembrane spanning element; these have integral kinase and guanylate cyclase domains. (05 Mar 2000) |
| B-cell antigen receptors | In the primary immune response immunoglobulin D and monomeric immunoglobulin M are the B-cell antigen receptors. On memory B-cells, other immunoglobulin molecules can serve as antigen receptors. (05 Mar 2000) |
| beta-adrenergic receptors | Adrenergic receptor's in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as propranolol, to block only some adrenergic receptor's and of other agents, such as isoproterenol, to activate only the same adrenergic receptor's. Such receptor's are designated as beta-receptors. Their activation results in physiological responses such as increases in cardiac rate and force of contraction (b1), and relaxation of bronchial and vascular smooth muscle (b2). (05 Mar 2000) |
| mannose-6-phosphate receptors | Receptors in Golgi apparatus to which newly synthesised proteins that are destined to enter lysosomes bind. (05 Mar 2000) |
| receptors, adrenergic | Cell-surface proteins that bind epinephrine and/or norepinephrine with high affinity and trigger intracellular changes. The two major classes of adrenergic receptors, alpha and beta, were originally discriminated based on their cellular actions but now are distinguished by their relative affinity for characteristic synthetic ligands. Adrenergic receptors may also be classified according to the subtypes of g-proteins with which they bind; this scheme does not respect the alpha-beta distinction. (12 Dec 1998) |
| receptors, adrenergic, alpha | One of the two major pharmacological subdivisions of adrenergic receptors. The alpha-beta distinction was originally based on cellular effects of receptor activation but now relies on the relative affinities for certain synthetic ligands. Alpha-adrenergic receptors are further subdivided into several subclasses based on studies of endogenous and cloned receptors. (12 Dec 1998) |
| receptors, adrenergic, alpha-1 | A subclass of alpha-adrenergic receptors (receptors, adrenergic, alpha). Alpha-1 adrenergic receptors can be pharmacologically discriminated, e.g., by their high affinity for the agonist phenylephrine and the antagonist prazosin. They are widespread, with clinically important concentrations in the liver, the heart, vascular, intestinal, and genitourinary smooth muscle, and the central and peripheral nervous systems. (12 Dec 1998) |
| receptors, adrenergic, alpha-2 | A subclass of alpha-adrenergic receptors (receptors, adrenergic, alpha). Alpha-2 adrenergic receptors can be pharmacologically discriminated, e.g., by their high affinity for the agonist clonidine and the antagonist yohimbine. They are found on pancreatic beta cells, platelets, and vascular smooth muscle, as well as both pre- and postsynaptically in the central and peripheral nervous systems. (12 Dec 1998) |
| receptors, adrenergic, beta | One of the two major pharmacologically defined classes of adrenergic receptors. The alpha-beta distinction was originally based on the cellular effects of receptor activation but now relies on the relative affinities for characteristic synthetic ligands. Beta adrenergic receptors are further subdivided based on information from endogenous and cloned receptors. (12 Dec 1998) |