Inhibition of NADH-methemoglobin reductase by organic phosphates

Karla Matteson, Fumito Taketa

Research output: Contribution to journalArticle

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Abstract

The organic phosphate allosteric effectors of hemoglobin, inositol hexaphosphate, 2,3-diphosphoglycerate, and ATP, interact with NADH-methemoglobin reductase (NADH-diaphorase). Significant inhibitory effects on the enzyme were found when dichlorophenolindophenol, or ferricyanide were used as electron acceptors in place of methemoglobin. In contrast, apparent stimulation of enzyme activity was observed when adult human methemoglobin was used as the electron acceptor. The latter is explained on the basis of the larger effect of the organic phosphate on the rate of reaction due to its interaction with the substrate methemoglobin to produce the favored T type of quaternary conformation. The inhibitory effect of inositol hexaphosphate on the enzyme is associated with a perturbation in the reactivity of essential sulfhydryl group(s) on the enzyme. It is suggested that the interaction of the organic phosphate with the enzyme as well as with the substrate is significant in determining the overall rate of methemoglobin reduction.

Original languageEnglish (US)
Pages (from-to)112-119
Number of pages8
JournalBBA - Enzymology
Volume571
Issue number1
DOIs
StatePublished - Nov 9 1979

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Cytochrome-B(5) Reductase
Organophosphates
Methemoglobin
Enzymes
Phytic Acid
2,6-Dichloroindophenol
Dihydrolipoamide Dehydrogenase
Electrons
2,3-Diphosphoglycerate
Hemoglobins
Adenosine Triphosphate

All Science Journal Classification (ASJC) codes

  • Medicine(all)

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Inhibition of NADH-methemoglobin reductase by organic phosphates. / Matteson, Karla; Taketa, Fumito.

In: BBA - Enzymology, Vol. 571, No. 1, 09.11.1979, p. 112-119.

Research output: Contribution to journalArticle

Matteson, Karla ; Taketa, Fumito. / Inhibition of NADH-methemoglobin reductase by organic phosphates. In: BBA - Enzymology. 1979 ; Vol. 571, No. 1. pp. 112-119.
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