Metabolic Bypass of the Tricarboxylic Acid Cycle during Lipid Mobilization in Germinating Oilseeds1 : Regulation of NAD+-Dependent Isocitrate Dehydrogenase Versus Fumarase

Biosynthesis of sucrose from triacylglycerol requires the bypass of the CO2-evolving reactions of the tricarboxylic acid (TCA) cycle. The regulation of the TCA cycle bypass during lipid mobilization was examined. Lipid mobilization in Brassica napus was initiated shortly after imbibition of the seed and proceeded until 2 d postimbibition, as measured by in vivo [1-14C]acetate feeding to whole seedlings. The activity of NAD+-isocitrate dehydrogenase (a decarboxylative enzyme) was not detected until 2 d postimbibition. RNA-blot analysis of B. napus seedlings demonstrated that the mRNA for NAD+-isocitrate dehydrogenase was present in dry seeds and that its level increased through the 4 d of the experiment. This suggested that NAD+-isocitrate dehydrogenase activity was regulated by posttranscriptional mechanisms during early seedling development but was controlled by mRNA level after the 2nd or 3rd d. The activity of fumarase (a component of the nonbypassed section of the TCA cycle) was low but detectable in B. napus seedlings at 12 h postimbibition, coincident with germination, and increased for the next 4 d. RNA-blot analysis suggested that fumarase activity was regulated primarily by the level of its mRNA during germination and early seedling development. It is concluded that posttranscriptional regulation of NAD+-isocitrate dehydrogenase activity is one mechanism of restricting carbon flux through the decarboxylative section of the TCA cycle during lipid mobilization in germinating oilseeds.

The NAD(P)H Dehydrogenase in Barley Thylakoids Is Photoactivatable and Uses NADPH as well as NADH1

An improved light-dependent assay was used to characterize the NAD(P)H dehydrogenase (NDH) in thylakoids of barley (Hordeum vulgare L.). The enzyme was sensitive to rotenone, confirming the involvement of a complex I-type enzyme. NADPH and NADH were equally good substrates for the dehydrogenase. Maximum rates of activity were 10 to 19 μmol electrons mg−1 chlorophyll h−1, corresponding to about 3% of linear electron-transport rates, or to about 40% of ferredoxin-dependent cyclic electron-transport rates. The NDH was activated by light treatment. After photoactivation, a subsequent light-independent period of about 1 h was required for maximum activation. The NDH could also be activated by incubation of the thylakoids in low-ionic-strength buffer. The kinetics, substrate specificity, and inhibitor profiles were essentially the same for both induction strategies. The possible involvement of ferredoxin:NADP+ oxidoreductase (FNR) in the NDH activity could be excluded based on the lack of preference for NADPH over NADH. Furthermore, thenoyltrifluoroacetone inhibited the diaphorase activity of FNR but not the NDH activity. These results also lead to the conclusion that direct reduction of plastoquinone by FNR is negligible.

The three-dimensional structure of NAD(P)H:quinone reductase, a flavoprotein involved in cancer chemoprotection and chemotherapy: mechanism of the two-electron reduction.

Quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2], also called DT diaphorase, is a homodimeric FAD-containing enzyme that catalyzes obligatory NAD(P)H-dependent two-electron reductions of quinones and protects cells against the toxic and neoplastic effects of free radicals and reactive oxygen species arising from one-electron reductions. These two-electron reductions participate in the reductive bioactivation of cancer chemotherapeutic agents such as mitomycin C in tumor cells. Thus, surprisingly, the same enzymatic reaction that protects normal cells activates cytotoxic drugs used in cancer chemotherapy. The 2.1-A crystal structure of rat liver quinone reductase reveals that the folding of a portion of each monomer is similar to that of flavodoxin, a bacterial FMN-containing protein. Two additional portions of the polypeptide chains are involved in dimerization and in formation of the two identical catalytic sites to which both monomers contribute. The crystallographic structures of two FAD-containing enzyme complexes (one containing NADP+, the other containing duroquinone) suggest that direct hydride transfers from NAD(P)H to FAD and from FADH2 to the quinone [which occupies the site vacated by NAD(P)H] provide a simple rationale for the obligatory two-electron reductions involving a ping-pong mechanism.

Nad Renem i nad Wisła, antyteza dziejowa.

"Przypisy [dokumenty] (głównie z Archiwum państwowego (Staatsarchiv) w Wiesbadenie)" in Polish or German: p. [231]-247.

Sulāfat al-nadīm fī al-muntakhabāt /

No more published?

Dějiny královského krajského města Písku nad Otavou /

Includes index.

Ikony Vsemilostivago Spasa i Pecherskoĭ Bozhīeĭ Materi nad Kremlevskimi Spasskimi vorotami v Moskvi͡e : Chasovni Spasiteli͡a i Smolenskoĭ Bozhīeĭ Materi u ėtikh vorot /

Cover title.

Nad Kodatsʹkym porohom (pro hetʹmana Ivana Sulymu); istorychne opovidannia.

Mode of access: Internet.

Sud pravdy nad sudom : di͡elo o G. Kvitnit͡skom v S.-Peterburgskom voenno-okruzhnom sudi͡e.

Mode of access: Internet.

Minutes of the right worshipful Grand lodge of the most ancient nad honorable fraternity of Free and accepted masons of Pennsylvania and masonic jurisdiction thereunto belonging. v. 1-12: 1779 to 1880.

Vols. 1-6 compiled by Joshua L. Lyte.

Piosnki wieśniacze z nad Dźwiny. Książeczka trzecia.

Mode of access: Internet.

Piosnki wieśniacze z nad Niemna i Dźwiny.

Mode of access: Internet.

Myśli o pismach polskich, z uwagami, nad sposobem pisania w rozmaitych materyach.

Errata slip inserted.

Uwagi nad Mateuszem herbu Cholewa, polskim XII wieku dzieiopisem, a w szczególności nad pierwszą dzieiów iego xięgą /

Bound with His Pszczoły i bartnictwo w Polszcze. Poznań, 1856.

Sud nad t︠s︡arevichem Aleksi︠e︡em Petrovichem : ėpizod iz zhizni Petra Velikago /

Mode of access: Internet.