Catechol O methyltransferase in rat erythrocyte and 3 other tissues: comparison of biochemical properties after removal of inhibitory calcium

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Abstract

The biochemical characteristics of soluble catechol O methyltransferase (COMT) activity in rat erythrocytes were compared with the properties of the soluble enzyme in rat liver, heart, and brain. COMT was measured by a procedure that avoided artifacts of some other assay procedures including inhibition of the enzyme by endogenous calcium. After the removal of calcium from the reaction mixture the apparent Michaelis Menten constants for the two cosubstrates of the COMT reaction, S adenosyl 1 methionine (SAM) and 3,4 dihydroxybenzoic acid (DBA), were similar in tissue preparations of rat liver, brain, heart and blood. The apparent Km values for the four tissues ranged from 5.7 to 6.7 x 10-6M and from 0.9-1.4 x 10-4M for SAM and DBA, respectively. The optimal pH and the optimal concentration of magnesium for the assay of red blood cell COMT were also similar to those for the enzyme in the three other rat tissues. After the removal of endogenous calcium, COMT activity in all four tissues was inhibited by the addition of calcium, and the [CaCl2] necessary to inhibit the enzyme activity 50% was 3-5 x 10-4M in all cases. The relative activities of COMT in the rat heart, brain, erythrocyte, and liver when expressed per g tissue or per ml of packed red blood cells were 1 to 1.15 to 1.58 to 140, respectively.

Original languageEnglish (US)
Pages (from-to)1197-1203
Number of pages7
JournalJournal of Neurochemistry
Volume27
Issue number5
StatePublished - 1976

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Catechol O-Methyltransferase
Rats
Erythrocytes
Tissue
Calcium
Liver
Brain
Blood
Enzymes
Methionine
Assays
Cells
Enzyme activity
Artifacts
Magnesium
Acids

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

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title = "Catechol O methyltransferase in rat erythrocyte and 3 other tissues: comparison of biochemical properties after removal of inhibitory calcium",
abstract = "The biochemical characteristics of soluble catechol O methyltransferase (COMT) activity in rat erythrocytes were compared with the properties of the soluble enzyme in rat liver, heart, and brain. COMT was measured by a procedure that avoided artifacts of some other assay procedures including inhibition of the enzyme by endogenous calcium. After the removal of calcium from the reaction mixture the apparent Michaelis Menten constants for the two cosubstrates of the COMT reaction, S adenosyl 1 methionine (SAM) and 3,4 dihydroxybenzoic acid (DBA), were similar in tissue preparations of rat liver, brain, heart and blood. The apparent Km values for the four tissues ranged from 5.7 to 6.7 x 10-6M and from 0.9-1.4 x 10-4M for SAM and DBA, respectively. The optimal pH and the optimal concentration of magnesium for the assay of red blood cell COMT were also similar to those for the enzyme in the three other rat tissues. After the removal of endogenous calcium, COMT activity in all four tissues was inhibited by the addition of calcium, and the [CaCl2] necessary to inhibit the enzyme activity 50{\%} was 3-5 x 10-4M in all cases. The relative activities of COMT in the rat heart, brain, erythrocyte, and liver when expressed per g tissue or per ml of packed red blood cells were 1 to 1.15 to 1.58 to 140, respectively.",
author = "Quiram, {D. R.} and Weinshilboum, {Richard M}",
year = "1976",
language = "English (US)",
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journal = "Journal of Neurochemistry",
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T1 - Catechol O methyltransferase in rat erythrocyte and 3 other tissues

T2 - comparison of biochemical properties after removal of inhibitory calcium

AU - Quiram, D. R.

AU - Weinshilboum, Richard M

PY - 1976

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N2 - The biochemical characteristics of soluble catechol O methyltransferase (COMT) activity in rat erythrocytes were compared with the properties of the soluble enzyme in rat liver, heart, and brain. COMT was measured by a procedure that avoided artifacts of some other assay procedures including inhibition of the enzyme by endogenous calcium. After the removal of calcium from the reaction mixture the apparent Michaelis Menten constants for the two cosubstrates of the COMT reaction, S adenosyl 1 methionine (SAM) and 3,4 dihydroxybenzoic acid (DBA), were similar in tissue preparations of rat liver, brain, heart and blood. The apparent Km values for the four tissues ranged from 5.7 to 6.7 x 10-6M and from 0.9-1.4 x 10-4M for SAM and DBA, respectively. The optimal pH and the optimal concentration of magnesium for the assay of red blood cell COMT were also similar to those for the enzyme in the three other rat tissues. After the removal of endogenous calcium, COMT activity in all four tissues was inhibited by the addition of calcium, and the [CaCl2] necessary to inhibit the enzyme activity 50% was 3-5 x 10-4M in all cases. The relative activities of COMT in the rat heart, brain, erythrocyte, and liver when expressed per g tissue or per ml of packed red blood cells were 1 to 1.15 to 1.58 to 140, respectively.

AB - The biochemical characteristics of soluble catechol O methyltransferase (COMT) activity in rat erythrocytes were compared with the properties of the soluble enzyme in rat liver, heart, and brain. COMT was measured by a procedure that avoided artifacts of some other assay procedures including inhibition of the enzyme by endogenous calcium. After the removal of calcium from the reaction mixture the apparent Michaelis Menten constants for the two cosubstrates of the COMT reaction, S adenosyl 1 methionine (SAM) and 3,4 dihydroxybenzoic acid (DBA), were similar in tissue preparations of rat liver, brain, heart and blood. The apparent Km values for the four tissues ranged from 5.7 to 6.7 x 10-6M and from 0.9-1.4 x 10-4M for SAM and DBA, respectively. The optimal pH and the optimal concentration of magnesium for the assay of red blood cell COMT were also similar to those for the enzyme in the three other rat tissues. After the removal of endogenous calcium, COMT activity in all four tissues was inhibited by the addition of calcium, and the [CaCl2] necessary to inhibit the enzyme activity 50% was 3-5 x 10-4M in all cases. The relative activities of COMT in the rat heart, brain, erythrocyte, and liver when expressed per g tissue or per ml of packed red blood cells were 1 to 1.15 to 1.58 to 140, respectively.

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