title: The oxidation of apomorphine and other catechol compounds by horseradish peroxidase: relevance to the measurement of dihydropteridine reductase activity.
abstract: It has been reported by Shen et al. (Shen, R.-S., Smith, R.V., Davis, P.J. and Abell, C.W. (1984) J. Biol. Chem. 259, 8894-9000) that apomorphine and dopamine are potent, non-competitive inhibitors of quinonoid dihydropteridine reductase. In this paper we show that apomorphine, dopamine and other catechol-containing compounds are oxidized rapidly to quinones by the horseradish peroxidase-H2O2 system which is used to generate the quinonoid dihydropterin substrate. These quinones react non-enzymatically with reduced pyridine nucleotides, depleting the other substrate of dihydropteridine reductase. When true initial rates of dihydropteridine reductase-dependent reduction of quinonoid dihydropterins are measured, neither apomorphine nor any other catechol-containing compound that has been tested has been found to inhibit dihydropteridine reductase.
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000378:metabolism* / Q000494:pharmacology; D002396:Catechols / Q000378:metabolism* / Q000494:pharmacology; D004093:Dihydropteridine Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000201:enzymology; D008722:Methods; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D051381:Rats; D012756:Sheep
chemical_list: D002396:Catechols; D009243:NAD; D006735:Horseradish Peroxidase; D010544:Peroxidases; D004093:Dihydropteridine Reductase; D009247:NADH, NADPH Oxidoreductases; D001058:Apomorphine; D004298:Dopamine