| substrate | <chemistry> A substance upon which an enzyme acts. Origin: L. Stratum = layer (18 Nov 1997) |
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| substrate cycle | <biochemistry> Any seqence of enzyme catalysed reactions in which the forward and reverse processes (catalysed by different enzymes) are consititutively active. Frequently used to describe the cycle of phosphorylation and dephosphorylation of phosphatidyl inositol derivatives in cell membranes. (05 Jan 1998) |
| substrate cycling | A set of opposing, nonequilibrium reactions catalyzed by different enzymes which act simultaneously, with at least one of the reactions driven by ATP hydrolysis. The results of the cycle are that ATP energy is depleted, heat is produced and no net substrate-to-product conversion is achieved. Examples of substrate cycling are cycling of gluconeogenesis and glycolysis pathways and cycling of the triglycerides and fatty acid pathways. Rates of substrate cycling may be increased many-fold in association with hypermetabolic states resulting from severe burns, cold exposure, hyperthyroidism, or acute exercise. (12 Dec 1998) |
| substrate inhibition | Inhibition of an enzyme activity by a substrate of the reaction catalyzed by that enzyme; often, this type of inhibition occurs at elevated substrate levels in which the substrate is binding to a second, non-active site on the enzyme. (05 Mar 2000) |
| substrate-level phosphorylation | Synthesis of high-energy phosphate bonds through reaction of inorganic phosphate with an activated (usually) organic substrate. (09 Oct 1997) |
| substrate specificity | A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. (12 Dec 1998) |
| suicide substrate | A competitive inhibitor that is converted to an irreversible inhibitor at the active site of the enzyme. Synonym: mechanism-based inhibitor. (05 Mar 2000) |
| insulin receptor substrate-1 protein | <chemical> Amino acid sequence given in first source; a 180 kD protein that contains multiple phosphorylated tyrosine residues after insulin stimulation; human and rat forms (hirs-1 and irs-1) are homologous Synonym: insulin receptor substrate-1-like protein, irs-1 protein, irs-1 gene product, hirs-1 protein, hirs-1 gene product, insulin receptor substrate 1, insulin receptor substrate-1 (05 Dec 1998) |
| enzyme-substrate complex | A noncovalent complex of two molecules; often referring to the enzyme-substrate complex in an enzyme-catalyzed reaction. Compare: central complex, Michaelis complex. Synonym: enzyme-substrate complex. (05 Mar 2000) |
| acute respiratory failure | Loss of pulmonary function either acute or chronic that results in hypoxaemia or hypercarbia. (05 Mar 2000) |
| adult respiratory distress syndrome | <chest medicine, syndrome> A clinical syndrome that includes pulmonary insufficiency. It is a descriptive term that is applied to a variety of diffuse infiltrative processes in the lung. Manifestations include severe shortness of breath, rapid breathing and arterial hypoxaemia (low oxygen). Chest X-ray shows bilateral diffuse infiltrates. Treatment most often includes mechanical respiratory support. Causes include toxic gas (chlorine, NO2, smoke) exposure, severe metabolic derangement, gastric acid aspiration, pancreatitis, sepsis and trauma. Acronym: ARDS (12 Jul 2000) |
| alkalosis, respiratory | A state due to excess loss of carbon dioxide from the body. (12 Dec 1998) |
| anti-allergic and respiratory system agents | A collective term for drugs used to treat allergic reactions as well as those drugs that produce an effect on the respiratory system. (12 Dec 1998) |
| Bell's respiratory nerve | <anatomy, nerve> Arises from the fifth, sixth, and seventh cervical nerves (roots of brachial plexus), descends the neck behind the brachial plexus, and is distributed to the serratus anterior muscle; it is somewhat unusual in that it courses on the superficial aspect of the muscle is supplies; its paralysis results in "winged scapula". Synonym: nervus thoracicus longus, Bell's respiratory nerve, external respiratory nerve of Bell, posterior thoracic nerve. (05 Mar 2000) |
| bovine respiratory syncytial virus | A pneumovirus causing an emerging disease in young cattle characterised by pneumonia, interstitial pulmonary oedema, and emphysema; sheep are also susceptible to the virus. (05 Mar 2000) |