| lipoprotein lipase | <enzyme> An enzyme of the hydrolase class that catalyses the reaction of triacylglycerol and water to yield diacylglycerol and a fatty acid anion. The enzyme hydrolyzes triacylglycerols in chylomicrons, very-low-density lipoproteins, low-density lipoproteins, and diacylglycerols. It occurs on capillary endothelial surfaces, especially in mammary, muscle, and adipose tissue. Genetic deficiency of the enzyme causes familial hyperlipoproteinaemia type I. Chemical name: Triacylglycero-protein acylhydrolase Registry number: EC 3.1.1.34 (12 Dec 1998) |
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| lipoprotein lipase deficiency, familial | A rare familial condition characterised by massive chylomicronaemia and decreased levels of other lipoproteins. It is due to deficiency of lipoprotein lipase, an alkaline triglyceride hydrolase which catalyses an important step in the extrahepatic removal of triglyceride-rich lipoproteins from the blood. (12 Dec 1998) |
| lipoprotein Lp(a) | A lipoprotein composed of an LDL particle combined with an additional protein, Lp(a) specific protein; elevated levels have been identified as a risk factor for coronary artery disease. (05 Mar 2000) |
| lipoprotein polymorphism | Heritable variations in low density beta-lipoproteins; the variant lipoproteins exhibit different antigenic and chemical properties when compared with normal lipoproteins. (05 Mar 2000) |
| lipoprotein-x | An abnormal lipoprotein which is present in large amounts in individuals suffering from obstructive liver diseases. It exists as a bilayer vesicle of equimolar phospholipids and unesterified cholesterol containing small amounts of plasma proteins (mainly albumin) in its internal aqueous compartment together with some apolipoproteins adsorbed on its surface. Separates with ldl by ultracentrifugation. (12 Dec 1998) |
| low density lipoprotein | <biochemistry> A lipoprotein substances (combination of a fat and a protein) which acts as a carrier for cholesterol and fats in the bloodstream. High levels of low density lipoprotein are considered a positive risk factor for the development of coronary artery disease. Less than 130 mg/dl is desirable, 130 to 159 mg/dl is borderline high, over 160 is considered high. Acronym: LDL (10 Jan 1998) |
| low density lipoprotein receptor | <biochemistry> A cell surface protein that mediates the endocytosis of low density lipoprotein by cells. Genetic defects in low density lipoprotein receptors lead to abnormal serum levels of low density lipoprotein and hypercholesterolaemia. (16 Mar 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) |