ZfN: Search Results

1	Author	Reinhard Jeck, Christoph Woenckhaus	Requires cookie*
	Title
	Abstract	The coenzyme anologues [3-(2-acetylpyridinio) -propyl]-adenosine pyrophosphate and [3-(2-bromo-acetylpyridinio) -propyl] -adenosine pyrophoshate were synthesized and used for inhibition studies. While the first compound reacts as competitive inhi bitor against NAD+ , the latter is able to form co valently bound derivatives of several NAD+ -depen-dent dehydrogenases, giving informations about amino acid side chains participating in the binding of the functional coenzyme part. [3-(2-acetylpyridinio) -propyl] -adenosine pyro phosphate exhibits strong hypochromicity between adenine and 2-acetylpyridine ring. Cleavage of the pyrophosphate bridge increases the absorption at 261 nm up to 22% and indicates, that the stacked configuration of the molecule is preferred in aqueous solution. In enzymatic assays with YADH and GAPDH [3-(2-acetylpyridinio) -propyl] -adenosine pyrophos phate acts as a competitive inhibitor against NAD+ . The inhibition constants are: Xi = 1.7'10-2 M (YADH) and 4.3, 10" 4m (GAPDH) and show, that the coenzyme analogue has little affinity to the co enzyme binding sites. Difference spectra of the coenzyme-enzyme mixtures and the isolated com ponents do not show any spectral changes due to the formation of the binary complex in the case of YADH and only small effects with GAPDH. From this results it can be concluded, that the incorpora tion of the 2-acetylpyridinio-propyl residue into the enzymes is sterically hindered. This is also indicated by the fact, that YADH shows smaller inhibition constants with adenosine monophosphate and adeno sine diphosphate 1. We obtained [3-(2-bromoacetylpyridinio) -pro pyl]-adenosine pyrophosphate by bromination of
	Reference	(Z. Naturforsch. 29c, 180 [1974]; received)
	Published	1974
	Keywords	) N AD+ -analogues, Dehydrogenases, Inhibition, Affinity Labelling
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	TEI-XML for	default:Reihe_C/29/ZNC-1974-29c-0180_n.pdf
	Identifier	ZNC-1974-29c-0180_n
	Volume	29

2	Author	Rainer Jaenicke, Hans-Dietrich Liidemann, Gerhard Schmid	Requires cookie*
	Title	Pressure, Temperature and pH Dependence of the Absorption Spectrum of Reduced Nicotinamide Adenine Dinucleotide
	Abstract	Enzymological studies at high hydrostatic pressure generally involve temperature, pH and pressure as variables, owing to the effect of adiabatic compression and the ionization volume o f the buffer system. In the case of N AD dependent oxidoreductases this implies that the extinction coefficient o f the coenzyme may be affected by p, T and pH, apart from the spectral change accompanying the redox reaction. Measurements o f the pressure dependence of the absorbance of N AD H show a slight red shift and a 1% decrease (3% increase) o f the absorbance at 339 nm (360 nm) at 2 kbar. The pH depen dence at the given wavelengths amounts to —(2.4 ± 0.1)% per pH unit (25 °C), while the intrinsic temperature effect (after correction for thermal expansion) is o f the order o f -0.2% per degree (2 0 -3 0 °C). Applying buffers with negligible ionization volume, 366 nm is the optimum wavelength for high pressure studies up to 2 kbar because here the pressure dependent spectral changes o f the N ADH absorption vanish.
	Reference	Z. Naturforsch. 36c, 84—8 (1981); received October 9 1980
	Published	1981
	Keywords	Absorption, Dehydrogenases, High Pressure, NADH, Oxidoreductases, pH Dependence, Tem perature Dependence
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	TEI-XML for	default:Reihe_C/36/ZNC-1981-36c-0084.pdf
	Identifier	ZNC-1981-36c-0084
	Volume	36