scholarly journals Structural and functional properties of a yeast xylitol dehydrogenase, a Zn2+-containing metalloenzyme similar to medium-chain sorbitol dehydrogenases

1998 ◽  
Vol 336 (1) ◽  
pp. 91-99 ◽  
Author(s):  
Regina LUNZER ◽  
Yasmine MAMNUN ◽  
Dietmar HALTRICH ◽  
Klaus D. KULBE ◽  
Bernd NIDETZKY
Keyword(s):  
Functional Properties ◽  
Initial Velocity ◽  
Chelating Agents ◽  
Product Inhibition ◽  
Xylitol Dehydrogenase ◽  
High Yield ◽  
Medium Chain ◽  
Structural And Functional Properties ◽  
The Stability ◽  
Sorbitol Dehydrogenases

The NAD+-dependent xylitol dehydrogenase from the xylose-assimilating yeast Galactocandida mastotermitis has been purified in high yield (80%) and characterized. Xylitol dehydrogenase is a heteronuclear multimetal protein that forms homotetramers and contains 1 mol of Zn2+ ions and 6 mol of Mg2+ ions per mol of 37.4 kDa protomer. Treatment with chelating agents such as EDTA results in the removal of the Zn2+ ions with a concomitant loss of enzyme activity. The Mg2+ ions are not essential for activity and are removed by chelation or extensive dialysis without affecting the stability of the enzyme. Results of initial velocity studies at steady state for d-sorbitol oxidation and d-fructose reduction together with the characteristic patterns of product inhibition point to a compulsorily ordered Theorell–Chance mechanism of xylitol dehydrogenase in which coenzyme binds first and leaves last. At pH 7.5, the binding of NADH (Ki ≈ 10 µM) is approx. 80-fold tighter than that of NAD+. Polyhydroxyalcohols require at least five carbon atoms to be good substrates of xylitol dehydrogenase, and the C-2 (S), C-3 (R) and C-4 (R) configuration is preferred. Therefore xylitol dehydrogenase shares structural and functional properties with medium-chain sorbitol dehydrogenases.

scholarly journals Further structural and functional properties of mini‒lipoxygenase, an active fragment of soybean lipoxygenase-1

2004 ◽  
Vol 18 (2) ◽  
pp. 331-338 ◽  
Author(s):  
Mauro Maccarrone ◽  
Almerinda Di Venere ◽  
Guus van Zadelhoff ◽  
Giampiero Mei ◽  
Gerrit Veldink ◽  
...  
Keyword(s):  
Functional Properties ◽  
Conformational Changes ◽  
Tertiary Structure ◽  
Catalytic Efficiency ◽  
Soybean Lipoxygenase ◽  
Binding Studies ◽  
Irreversible Inhibitor ◽  
Structural And Functional Properties ◽  
The Stability ◽  
Induced Changes

Lipoxygenases (Loxs) form a homologous family of non-heme, non-sulfur iron containing lipid-peroxidizing enzymes, which catalyze the dioxygenation of polyunsaturated fatty acids to the corresponding hydroperoxy derivatives. Soybean lipoxygenase-1 (Lox-1) is widely used as a prototype for studying the structural and functional properties of lipoxygenases. Tryptic digestion of soybean Lox-1 is known to produce a 60 kDa fragment, termed “mini-Lox”, which shows enhanced catalytic efficiency and higher membrane binding ability than the native enzyme (M. Maccarrone, M.L. Salucci, G. van Zadelhoff, F. Malatesta, G. Veldink, J.F.G. Vliegenthart and A. Finazzi-Agrò,Biochemistry40(2001), 6819–6827). In this study, we have investigated the stability of mini-Lox in guanidinium hydrochloride (GdHCl) and under high pressure by fluorescence and circular dichroism spectroscopy. The denaturation experiments demonstrate that mini-Lox is a rather unstable molecule, which undergoes a two-step unfolding transition. Both chemical- and physical-induced denaturation suggest that mini-Lox is more hydrated than Lox-1, an observation also confirmed by 1-8 anilinonaphtalene sulphonic acid binding studies. We have also investigated the occurrence of substrate-induced changes in the protein tertiary structure by fluorescence techniques. In particular, eicosatetraynoic acid (ETYA), an irreversible inhibitor of lipoxygenase, has been used to mimic the effect of substrate binding. We demonstrated that mini-Lox is indeed characterized by much larger conformational changes than those occurring in the native Lox-1 upon binding of ETYA. All these findings strongly support the hypothesis that the larger hydration of mini-Lox renders this molecule more flexible and therefore less stable, that on the other hand is probably causing its higher catalytic efficiency.

Structural and functional properties of Escherichia coli-derived nucleoplasmin A comparative study of recombinant and natural proteins

2001 ◽  
Vol 268 (6) ◽  
pp. 1739-1748
Author(s):  
Aitor Hierro ◽  
Jesus M. Arizmendi ◽  
Javier De Las Rivas ◽  
M. Angeles Urbaneja ◽  
Adelina Prado ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Comparative Study ◽  
Functional Properties ◽  
Structural And Functional Properties

Characterization and functional properties of new everbearing strawberry (Fragaria x ananasa Duch.) cultivar, ‘Summertiara’ berries

2014 ◽  
Vol 4 (1) ◽  
pp. 1 ◽  
Author(s):  
Takeshi Nagai ◽  
Misuzu Tamai ◽  
Masato Sato ◽  
Yasuhiro Tanoue ◽  
Norihisa Kai ◽  
...  
Keyword(s):  
Vitamin C ◽  
Sensory Evaluation ◽  
Functional Properties ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Antihypertensive Activity ◽  
Oxygen Species ◽  
Total Anthocyanins ◽  
Strawberry Cultivar ◽  
The Stability

Background: In recent years, a new everbearing strawberry cultivar, ‘Summertiara’ was cultivated to supply the strawberries in pre-harvest season from July to October in Japan. For highly research and development of processing of this cultivar, ‘Summertiara’ berries, the objective of this study was to characterize these berries, with relation to chemical parameters, total phenols, total flavonoids, total vitamin C, and total anthocyanins, and was to investigate the solubility and the stability of anthocyanins from the berries. Moreover, the functional properties such as antioxidative activity, active oxygen species scavenging activity, and antihypertensive activity were also evaluated.Methods: Chemical analysis, colour measurement, and sensory evaluation of new everbearing strawberry cultivar, ‘Summertiara’ berries were performed. Next, the solubility of anthocyanins from the berries and stability of these against pH, temperature, and an incandescent lighting were investigated. Moreover, functional properties of the extracts prepared from berries were elucidated using 5 different methods.Results: The contents of water, proteins, lipids, carbohydrates, and ash were the same as those of other cultivar berries. The sugar-acid ratio in the berries was low; these were acidulous. By sensory evaluation, the main factors were vivid red colour, aroma, and acidity. The berries were rich in phenols, flavonoids, vitamin C, and anthocyanins. The anthocyanins of the berries became unstable by heat treatment and light exposures such as visible rays. On the other hand, the extracts prepared from the berries showed the functionalities such as antioxidant activity, active oxygen species scavenging activities, and antihypertensive activity.  Conclusions: The strawberry cultivar, ‘Summertiara’ berries were the most suitable for processing ingredient of strawberry-derived products with superior health promoting functionalities.Keywords: Summertiara, everbearing strawberry cultivar, characterization, sensory evaluation, color and storage, functional property

scholarly journals VARIABILTY AND STABILTY OF TUBER YIELD OF JERUSALEM ARTICHOKE (Helianthus tuberosus L.) / VARIABILIDAD Y ESTABILIDAD DEL RENDIMIENTO DE TUBERCULOS DEL TOPINAMBO / VARIABILITÉ ET STABILITÉ DU RENDEMENT DU TUBERCULE DE TOPINAMBUR

Helia ◽  
2001 ◽  
Vol 24 (35) ◽  
pp. 25-32 ◽  
Author(s):  
Janoš Berenji ◽  
Vladimir Sikora
Keyword(s):  
Tuber Yield ◽  
Jerusalem Artichoke ◽  
Tuber Size ◽  
Yield Stability ◽  
Tuber Number ◽  
High Yield ◽  
Helianthus Tuberosus ◽  
Variety Trial ◽  
Stable Performance ◽  
The Stability

SUMMARYThe objective of this paper was to estimate the genetic and ecological variation as well as the stability of tuber yield per plant, tuber number per plant and tuber size of Jerusalem artichoke based on the results of a variety trial carried out with 20 different Jerusalem artichoke varieties during the period of 1994-2000. Significant genetic as well as ecologycal variation was observed for all of the traits studied. The most promissing varieties showing high tuber yield combined with high yield stability were “BT-4”, “Violet Rennes” and “UKR 4/ 82”. It is encouraging that the highest yielding varieties exibited a rather stable performance over environments.

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