Protein-bound mono(ADP-ribose) residues were quantitated in the livers of nicotinamide-treated and control rats. Nicotinamide administration led to a rise in NAD® (2.5-fold) and in protein-bound mono (ADP-ribose) residues (1.5-fold). This increase was higher in the NH 2 OH-sensitive mono(ADP-ribose) protein conjugates than in the NH 2 OH-resistant subfraction. NADH, NADP and NADPH levels did not change significantly under these conditions.The findings show that nicotinamide induced an increased ADP ribosylation of new acceptor sites, and not merely an elongation of pre-existing (ADP-ribose)fl chains. A correlation of the NAD® concentration and the extent of postsynthetic modification of nuclear proteins by mono(ADP-ribose) residues was not restricted to nicotinamide-induced changes. It was also seen in various tissues with widely differing NAD® levels.
T h e enzyme phenylalanine-ammonia-lyase (PAL) could be detected in six ce11 lines of D a u c u s Caro t a L. which differ in their ability t o synthetize anthocyanins. In those ce11 lines which do not produce anthocyanins in the dark, PAL activity is enhanced by light. With one exception this is paralleled by anthocyanin biosynthesis. 2.4-dichlorophenoxy acetic acid delays PAL activity and anthocyanin or chlorogenic acid accumulation. l n three other ce11 lines which are able t o produce anthocyanins under special conditions in the dark, too, PAL activity is not enhanced by light, although anthocyanin production is increased or in one case even induced. It is concluded that at least in those latter ce11 lines anthocyanin biosynthesis is not regulated by PAL but by an enzyme which is located later on in the biosynthetic pathway.Heruntergeladen von: National University of Singapore. Urheberrechtlich geschützt.
1) During a treatment of rats with 4 mmol of nicotinamide per kg body weight daily at 12-h intervals for several weeks a permanent rise of liver NAD by several hundred percent is effected; NADP® + NADPH also increase slightly. 2) Male and female animals of the SIV-50 strain differ in normal and in elevated NAD® values; female rats react more markedly and present more pronounced alterations of the liver. 3) Besides nicotinamide, large amounts of " 1methylnicotinamide and nicotinuric acid, and also small amounts of nicotinamide TV-oxide are excreted into the urine. Nicotinuric acid, an unexpected metabolite, was crystallized from urine and identified unequivocally. 4) A permanent load of rats with l g nicotinamide per kg body weight daily leads to alterations of the liver which manifest themselves macroscopically, by hepatocyte enlargement, glycogen deposits, enzyme decreases, and eventually fatty degeneration. When extra methionine and glycine are given in the diet, liver alterations are much less severe. It is concluded that the treatment with nicotinamide causes a severe amino acid imbalance. 5) During the treatment, animals show symptoms of catatonic stupor which is discussed in connection with proposals of a nicotinamide megatherapy against schizophrenia. On the whole, the experimental system of permanently elevated NAD® concentrations is combined with rather serious disadvantages; it is not regarded as a very good general model in studies of liver NAD®.
Nuclei isolated from rat liver were incubated with NAD whose two ribose moieties were respectively labeled with 3H or 14C. By enzymatic (phosphodiesterase) and/or chemical (hydroxylamine) attack on doubly labeled ADP-ribosylated nuclear residues, AMP was found after hydroxylaminolysis as well as iso-ADP-ribose after phosphodiesterase plus hydroxylamine, in the absence of detectable amounts of ribose-5-phosphate. This is taken to indicate the existence of additional ribose-protein binding sites in in vitro ADP-ribosylated nuclear proteins: Besides C-1" (Hayaishi et al., Stocken et al.) C-2' and/or C-3' (purine-near) as well as C-2" and/or C-3" (pyrimidine-near), not only at the end but also within the chain of oligo-ADPR.
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