Showing papers on "Catechol-O-methyl transferase published in 1973"
TL;DR: The 64% reduction in myocardial noradrenaline in patients with congestive failure was related directly to a 54% reduce in tyrosine hydroxylase activity and inversely to an 88% increase in mean wedge pulmonary artery pressure.
Abstract: Biopsies of myocardium were obtained from patients with acquired and congenital heart disease at the time of cardiopulmonary bypass and assayed for content of noradrenaline and the activities of the rate limiting biosynthetic enzyme — tyrosine hydroxylase, and the degradative enzymes — monoamine oxidase and catechol-0-methyl transferase (COMT). The 64% reduction in myocardial noradrenaline in patients with congestive failure was related directly to a 54% reduction in tyrosine hydroxylase activity and inversely to an 88% increase in mean wedge pulmonary artery pressure. The activity of the extraneuronal enzyme, COMT, was increased 115% in hearts of those with congestive failure, due in part to fibrotic replacement of innervated contractile muscle.
70 citations
TL;DR: A simple spectrophotometric assay for COMT activity can be monitored continuously using a coupled enzyme assay based on the difference in the ultraviolet absorption spectra between SAH and SIH.
39 citations
TL;DR: Activity in erythrocytes, which was 10 times greater in rats than in humans when optimal assay conditions were used, was unaffected by L-dopa treatment, and the lack of adaptive increases in COMT may explain, in part, the observed lack of “fall-off” in the therapeutic efficacy of L- dopa.
25 citations
01 Jan 1973
TL;DR: Present evidence suggests that at least two other forms of COMT with molecular weights of 11,250 and 37,000 are present in the soluble fraction from rat liver.
Abstract: Publisher Summary This chapter discusses a study examining immunological characterization of catechol-O-methyltransferase (COMT). Rabbits immunized with pure COMT EC. 2.1.1.6, responded by forming first one and later three distinct populations of enzyme-related antibodies. The antisera were shown to precipitate and neutralize the enzyme. The enzyme protein used for the immunization was obtained from the soluble fraction of rat liver, followed by affinity chromatography on Agarose 4B to which dopamine was attached through the amine group, gel filtration on Sephadex G-100 and filtration through an Amicon PM-30 membrane. While this form of COMT was chosen as the antigen, present evidence suggests that at least two other forms of COMT with molecular weights of 11,250 and 37,000 are present in the soluble fraction from rat liver. Rabbits were immunized by intramuscular injection of 0.4 mg antigen in CFA at day 0 followed by 0.4 mg in inc.FA at day 14, and thereafter repeated subcutaneous injections of 0.4 mg antigen in PBS at two-week intervals. Antisera obtained subsequent to subcutaneous administration of the antigen show the gradual appearance of two additional COMT-related antibody populations.
20 citations
TL;DR: The postnatal development of three enzymes in the rat forebrain was studied and the increase in the enzyme activities in the subcellular fractions which contained the main part of the different enzymes was still 2–4‐fold for COMT and LDH while for MAO it was 4‐fold.
Abstract: — The postnatal development of three enzymes in the rat forebrain was studied. When expressed per tissue weight the catechol-O-methyl transferase (COMT) increased 2-fold from birth to adult age, the lactate dehydrogenase (LDH) 4-fold and the monoamine oxidase (MAO) 12-fold. Expressed per mg protein the increase in the enzyme activities in the subcellular fractions which contained the main part of the different enzymes was still 2–4-fold for COMT and LDH while for MAO it was 4-fold.
There was a relative increase in the COMT activity in the P2 fraction (synaptosomes and mitochondria). This increase was identical with a corresponding increase in LDH activity and protein and was probably due to growth of nerve terminals. The COMT in the cytoplasm of the synaptosomes showed the same increase relative to the proteins as did the ‘free’ cytoplasmic enzyme.
The conclusion is drawn that the enzymes in the rat brain show a certain degree of development during brain growth. An additional increase of some enzymes is due to the development of specialized structures such as mitochondria and nerve terminals with synapses. COMT is not related to any such specialized structure.
18 citations
TL;DR: These results are in agreement with earlier findings which have shown that rat reticulocytes contain a complete adrenergic β-receptor-effector system.
Abstract: Catecholamine inactivating enzymes in red blood cells are preferentially localized in the reticulocytes and not in mature erythrocytes: catechol-O-methyltransferase (COMT) activity in erythrocyte ghost preparations from reticulocyte-rich blood of rats pretreated with acetyl-phenylhydrazine was found to be 5 times higher than in ghosts from reticulocyte-poor blood. In the respective 12000×g supernates of the haemolysates, COMT activity in reticulocyte-rich preparations was not significantly enhanced. Significant monoamine oxidase (MAO) activity was only found in ghosts from reticulocyte-rich blood prepared by centrifugation at 12000×g. MAO activity was inhibited in vitro by pargyline concentrations<10−6 M.
10 citations
01 Jan 1973
TL;DR: This chapter elaborates some findings on catechol-O-methyltransferase (COMT), which is able to methylate all the compounds which have a catechols function.
Abstract: Publisher Summary This chapter elaborates some findings on catechol-O-methyltransferase (COMT). COMT is able to methylate all the compounds which have a catechol function. In vivo catecholamines are catabolized by COMT and by mono-aminoxydase (MAO). During the purification of soluble COMT from rat liver two or three fractions with COMT, activities were observed. These fractions can be obtained by electrophoresis or chromatographic methods at various steps of the purification. This problem of isozymes has been studied using isoelectrofocusing, a very high resolution system for the separation of proteins based on the differences between isoelectric pH (pHi). Many inhibitors of COMT have been described, but almost all belong to the group of catechol compounds with an inhibition of a competitive type. Some other compounds that have been studied have been gallic acid derivatives.
7 citations
TL;DR: Catechol-O-methyltransferase (COMT) was found in the circum-oesophageal, cerebral and visceral ganglia of Helix aspersa using a radioactive assay and the enzyme was also present in the heart and hepatopancreas.
Abstract: 1. 1. Catechol-O-methyltransferase (COMT) was found in the circum-oesophageal, cerebral and visceral ganglia of Helix aspersa using a radioactive assay. The enzyme was also present in the heart and hepatopancreas. The highest activity was found in the hepatopancreas and the lowest in the cerebral ganglia. 2. 2. Over 75 per cent of the total COMT activity of the hepatopancreas was recovered in the high-speed supernatant fraction with only trace amounts in the crude nuclear, mitochondrial and microsomal fractions. Similar results were obtained in the circum-oesophageal ganglia. 3. 3. The results are discussed in relation to the function of the enzyme in the inactivation of catecholamines and the supposed cellular localization of catechol-O-methyltransferase.
7 citations