Erythrocyte catechol-O-methyltransferase Activity Research Articles

The Inheritance of human erythrocyte catechol‐O‐methyltransferase activity

Erythrocyte catechol‐O‐methyltransferase (COMT) activity was analyzed in 107 individuals from 23 families. The observed activities were consistent with an autosomal codominant inheritance of the gene coding for erythrocyte COMT activity.

Catechol-O-methyltransferase of erythrocytes in patients with endogenous psychoses

A significant decrease in catechol- O-methyltransferase (COMT) activity of erythrocytes was found in both male and female schizophrenic patients, as well as in male patients with schizophreniform psychosis. Among control subjects, a sex difference in COMT activity of erythrocytes was found, with males showing significantly higher activity than females. It is suggested that a genetically determined deficiency of catecholamine degradative enzymes in the central nervous system or, alternatively, influences of nongenetic hormonal factors could be implicated in the findings of altered erythrocyte COMT activity reported.

Catechol-O-methyltransferase activity in human erythrocytes: methodological aspects.

Different methodological aspects on the assay of human erythrocyte catechol-O-methyltransferase (COMT) activity were studied. No temporal variations were found either over a 24 hour period or over one month. Erythrocytes from whole blood collected with any of the anticoagulants heparin, EDTA or citrate could be used as the enzyme source provided the cells were washed in saline. The COMT activity in lysed erythrocytes was rapidly lost when the lysate was stored at +4 degrees C and -20 degrees C. Intact erythrocytes could be stored up to one week in +4 degrees C without considerable loss of activity. The COMT activity was stable for at least two years when storing the cells at -85 degrees C. Freeze-thawing and hypotonic disruption of the erythrocytes resulted in the same activity and neither freeze-thawing nor sonication altered the apparent Km for the substrate. Noradrenaline and 3,4-dihydroxybenozic acid (DBA) could both be used as substrates although DBA gave higher activity values and had a higher affinity to the enzyme. The COMT activity increased with increasing concentration of the methyl-donor S-adenosyl-1-methionine up to approximately 0.1 mM. Preincubation at 47 degrees C decreased the COMT activity whereas the apparent Km values remained unchanged. The present COMT assay was convenient and reproducible and could be used with small amounts of blood with different kinds of anticoagulants. Interactions with plasma factors were avoided by washing the erythrocytes with isotonic sodium chloride.

Human erythrocyte catechol-o-methyltransferase: Correlation with lung and kidney activity

Catechol-O-methyltransferase (COMT) activity measured in homogenates of human lung or renal cortical tissue was approximately an order of magnitude greater than the enzyme activity in human erythrocytes. Lung and blood enzyme activities varied from individual to individual over a 5–7 fold range. There was a highly significant correlation between the COMT activity in erythrocytes and the enzyme activity in lung (r = 0.59, P < .001, N = 29) and kidney (r = 0.81, P < .005, N = 12) of the same subjects. These results suggest that the relative COMT activity in lung and kidney might be predicted by the measurement of the enzyme activity in blood and raise the possibility that individual variation in the metabolism of endogenous catecholamines and catechol drugs in man may result in part from variations in COMT activity.

Catechol-O-methyltransferase activity in erythrocytes of children with autism

1. The activity of the enzyme catechol-O-methyltransferase (COMT) was determined in the erythrocytes of normal and autistic children. 2. There was no difference in enzyme activity between the two groups, although in both the normal and autistic females the erythrocyte COMT activity showed considerable within-group variation. 3. When the erythrocyte homogenates were divided into particulate and soluble fractions, some differences were observed. The COMT activity in the soluble fraction was less in erythrocytes from autistic males than in those from control males, whereas that in autistic females was higher than in those from control females.

Effects of the tumor inhibitor, vernolepin, and of its thioether adduct, on the activity of catechol O-methyltransferase in vitro

The activity of cat erythrocyte lysate catechol O-methyltransferase (COMT) in vitro is shown to be amenable to control by a variety of reagents including an SH reactive tumor inhibitor (vernolepin), its non-SH reactive derivative (the bis- n-propanethiol adduct of vernolepin), n-propanethiol itself, and the organic solvent, methanol. The ability of the adduct to modify COMT activity extends to all other sources examined (partially purified rat liver COMT and 78,000 g supernatant from rat liver, kidney, spleen and brain). Alterations in kinetic parameters (apparent K m and Vmax) were observed when the adduct of vernolepin enhanced cat erythrocyte COMT activity.