| beta-hydroxybutyric acid | CH3CH(OH)CH2COOH;the d-stereoisomer is one of the ketone bodies and is formed in ketogenesis; it is an important fuel for extrahepatic tissues; as an acyl derivative it is also an intermediate in fatty acid biosynthesis. The l-isomer is found as a coenzyme A derivative in b oxidation of fatty acids. Synonym: 3-hydroxybutanoic acid, beta-hydroxybutyric acid. D-3-hydroxybutyric acid dehydrogenase, an enzyme that reversibly catalyses the interconversion of the two main ketone bodies, catalyzing acetoacetate + NADH + H+ &dblarr; d-3-hydroxybutyrate + NAD+. (05 Mar 2000) |
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| beta-hydroxyisobutyric acid | HOCH2CH(CH3)COOH;an intermediate in the degradation of l-valine. (05 Mar 2000) |
| beta-hydroxypropionic acid | A minor intermediate in propionate and methylmalonate metabolism. See: beta-hydroxypropionic aciduria. (05 Mar 2000) |
| beta-hydroxypropionic aciduria | Elevated levels of beta-hydroxypropionic acid in the urine; seen in defects in methylmalonic acid and propionate metabolism, as well as in ketotic hyperglycinaemia syndrome. (05 Mar 2000) |
| beta-hypophamine | <protein> A peptide hormone released from the posterior pituitary lobe but synthesised in the hypothalamus. There are 2 forms, differing only in the amino acid at position 8: arginine vasopressin is widespread, while lysine vasopressin is found in pigs. Has antidiuretic and vasopressor actions. Used in the treatment of diabetes insipidus. (18 Nov 1997) |
| beta interferon | A protein liberated by fibroblasts in response to a viral infection. (27 Sep 1997) |
| beta-ketoacyl-ACP reductase | A part of the fatty acid synthase complex; an enzyme reversibly reacting 3-oxoacyl-ACP with NADPH to form d-3-hydroxyacyl-ACP and NADP+. Synonym: beta-ketoacyl-ACP reductase. (05 Mar 2000) |
| beta-ketoacyl-ACP synthase | <enzyme> An enzyme condensing malonyl-ACP and acyl-cys-protein to 3-oxoacyl-ACP + cys-protein + CO2, and similar reactions, as steps in fatty acid synthesis; cys-protein is also a part of the fatty acid synthase complex. Synonym: acyl-malonyl-ACP synthase, beta-ketoacyl-ACP synthase. (05 Mar 2000) |
| beta-ketoadipyl-coenzyme A thiolase | <enzyme> Last enzyme in the beta-ketoadipate pathway in pseudomonas putida; genbank l33795 Registry number: EC 2.3.1.- Synonym: pcaf gene product, beta-ketoadipyl-CoA thiolase (26 Jun 1999) |
| beta-ketohydrogenase | Beta-Hydroxyacyl dehydrogenase;enzyme catalyzing the oxidation of an l-3-hydroxyacyl-CoA to a 3-ketoacyl-CoA with reduction of NAD+; one of the enzymes of the b oxidation of fatty acids. Synonym: beta-ketohydrogenase, beta-ketoreductase. (05 Mar 2000) |
| beta-ketoreductase | Beta-Hydroxyacyl dehydrogenase;enzyme catalyzing the oxidation of an l-3-hydroxyacyl-CoA to a 3-ketoacyl-CoA with reduction of NAD+; one of the enzymes of the b oxidation of fatty acids. Synonym: beta-ketohydrogenase, beta-ketoreductase. (05 Mar 2000) |
| beta-ketothiolase | <enzyme> An enzyme catalyzing the thioclastic cleavage by coenzyme A of beta-ketoacyl-CoA, forming an acyl-CoA with a carbon chain shorter by two atoms, the missing two atoms appearing as acetyl-CoA. A step in fatty acid degradation. See: acetyl-CoA acetyltransferase. Synonym: 3-ketoacyl-CoA thiolase, beta-ketothiolase. (05 Mar 2000) |
| beta-lactam | <pharmacology> A class of broad spectrum antibiotics that are structurally and pharmacologically related to the penicillins and cephalosporins. (05 Mar 2000) |
| beta-lactamase | <enzyme> An enzyme produced by some bacteria, which causes the breakdown of the active form of some penicillin antibiotics, rendering them ineffective. It causes the hydrolysis of a beta-lactam (as penicillin to penicilloic acid); found in most strains of staphylococcus bacteria that are naturally resistant to penicillin. Synonym: cephalosporinase, penicillinase. (05 Mar 2000) |
| beta-lactamase inhibitor | <pharmacology> Drugs such as clavulanic acid, which are used to inhibit bacterial beta-lactamases; often used with a penicillin or cephalosporin to overcome drug resistance. (05 Mar 2000) |