Posted by qqqsimmons on November 4, 2006, at 12:23:57
In reply to Re: resveratrol improves lifespan, makes you manic, posted by linkadge on November 4, 2006, at 10:38:51
thanks for the info.
i wonder if consuming lots of calcium also inhibits COMT:
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Calcium inhibition of rat liver catechol-O-methyltransferase*1Abstract
The activity of partially purified rat liver catechol-O-methyltransferase (COMT) was measured by an assay procedure in which 3,4-dihydroxybenzoic acid was used as a substrate for the enzyme. Optimal enzyme activity was present at a concentration of MgCl2 of 10−3 M. The effects on COMT activity of a series of alkaline earth compounds were determined in the presence of optimal concentrations of MgCl2. CaCl2 and Ca(NO3)2 at concentrations of 10−3 M reduced COMT activity by 63 and 59 per cent respectively. BaCl2 and Sr(NO3)2 (10−3 M) did not decrease enzyme activity, nor did additional MgCl2 to a final [Mg2+] of 2 × 10−3 M) did not decrease enzyme activity and 0·50 × 10−3 M CaCl2 in the presence of different concentrations of 3,4-dihydroxybenzoic acid, S-adenosyl-1-methionine and MgCl2 was determined. In each case Lineweaver-Burk plots of these data were compatible with noncompetitive or “mixed” inhibition.###
Catechol-o-methyltransferase in rat erythrocyte and three other tissues: comparison of biochemical properties after removal of inhibitory calcium.Quiram DR, Weinshilboum RM.
Clinical Pharmacology Unit, Departments of Pharmacology and Internal Medicine, Mayo Foundation, Rochester, MN 55901, USA.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(-6) M and from 0.9-1.4 x 10(-4) M 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(-4) M 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.
> Alzheimers drugs like aricept are acetylcholinsterase inhibitors. Acetylcholinsterase degreades acetycholine, so an acetycholnsterase inhibitor prolongs the life of acetycholine, which is supposed to affect some aspects of human memory.
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> Linkadge
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