Lung contains an inhibitor for nicotinatemononucleotide pyrophosphorylase (carboxylating) of NAD biosynthesis |
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Authors: | R L Seither O R Brown B V Babu |
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Institution: | John M. Dalton Research Center, Columbia, MO. |
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Abstract: | Rat, cow and foal lung extracts contained an inhibitor for the liver NAD biosynthetic-pathway enzyme, nicotinatemononucleotide pyrophosphorylase (carboxylating) EC 2.4.2.19]. The inhibitor was not dialyzable, was labile at 100 degrees C, was retained by a 30,000 dalton pore size Amicon membrane and, when partially purified by precipitation at 40-100% ammonium sulfate, inhibited the enzyme stoichiometrically. Lung reportedly does not contain nicotinate-mononucleotide pyrophosphorylase or make NAD de novo. However, the inhibitor would mask detection of the enzyme in lung extracts. We detected a low nicotinatemononucleotide pyrophosphorylase-like activity (0.003 +/- 0.001 nanomoles CO2 produced from quinolinic acid per mg of extract protein) in rat lung but none in foal or cow lung. |
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