Purification and Properties of NAD(P)H:(quinone-acceptor) Oxidoreductase of Sugarbeet Cells

Autor:	Patrizia Bonora, Paolo Trost, Paolo Pupillo, Sandra Scagliarini
Rok vydání:	1995
Předmět:	chemistry.chemical_classification Stereochemistry Dehydrogenase Fast protein liquid chromatography Plants Biochemistry Duroquinone chemistry.chemical_compound Glycerol-3-phosphate dehydrogenase NAD(P)H dehydrogenase chemistry Oxidoreductase NAD+ kinase Ferricyanide Quinone Reductases
Zdroj:	European Journal of Biochemistry. 234:452-458
ISSN:	1432-1033 0014-2956
DOI:	10.1111/j.1432-1033.1995.452_b.x
Popis:	NAD(P)H :(quinone-acceptor) oxidoreductase [NAT)(P)H-QR], a plant cytosolic protein, was purified froni cultured sugarbeet cells by a combination of ainnlonium sulfatc fractionation, FPLC Superdex 200 gel filtration, Q-Sepharosc anion-cxchange chromatography, and a final Blue Sepharose CL-6B affinity chromatography with an NADPH gradient. The subunit molecular niass is 24 kDH and thc activc protein (94 kna) is a tetrarner. The isoelectric point is 4.9. The enzyme was churactcrized by ping-pong kinetics and extremely elevated catalytic capacity. It prcfcrs NADPH over NADH as electron donor (k,,, lK,,, ratios of 1.7X108 M-I s-' and 8.3X lo7 M-' s-! for NADPH and NADH, respectively, with benzoquinoiie as clcctron acccptor). Thc acridonc derivativc 7-iodo-acridone-4-carboxylic acid is an efficient inhi bitor M). dicurnarol is weakly inhibitory. The best acceptcx substrates are hydrophilic, shortchain quinoncs such :IS ubiquinonc-0 (Q-O), bcnzoquinonc and menndione, followed by duroquinone and ferricyanide, whereas hydrophobic quinones, cytochronie I: and oxygen are reduced at negligible rates at best. Quinone acceptors are reduced by a two-electron reaction with no apparent release of free semiquinonic intermediates. ?'his and the above properties suggesr some relationship of NAD(P)H-QR to DTdiaphorase, an animal flavoprotein which, however, has distinct structural properties and is strongly inhibited by dicumarol. It is proposed that NAD(P)H-QR by scavenging unreduced quinones and making thein prone to conjugation may act in plant tissues as a functional equivalent of DT-diaphorase. Ke-ywords: NAD(P)H: (quinone-acceptor) oxidoredudase; DT-diaphorase; quinones: NAD(P)H dehydrogenase; Beta vulgaris. = SX
Databáze:	OpenAIRE
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