A Dpnh-Specific Nitrate Reductase From Germinating Wheat

1959 ◽  
Vol 12 (2) ◽  
pp. 181 ◽  
Author(s):  
D Spencer
Keyword(s):  
Nitrate Reductase ◽  
Flavin Adenine Dinucleotide ◽  
Potassium Cyanide ◽  
Fold Increase ◽  
Maximum Activity ◽  
Flavin Mononucleotide ◽  
Enzyme Complex ◽  
Soluble Enzyme ◽  
Ph Optimum ◽  
Isolation And Purification

The isolation and purification of a nitrate reductase from the embryos of germinating wheat is described. This is a soluble enzyme, which is coupled specifically to reduced diphosphopyridine nucleotide (DPNH). Addition of flavin adenine dinucleotide to the purified enzyme results in a three-fold increase in activity. Flavin mononucleotide is without effect. Potassium cyanide and sodium azide cause 50 per cent. inhibition of enzyme activity at 1� 6 X IO-6M and 2 X IO-5M respectively. The effect of a range of other inhibitors is reported. The presence of inorganic phosphate is required for maximum activity. The dissociation constant (Ks ) of the nitrate-enzyme complex is 3�8 X IO-4M, and that of the DPNH-enzyme complex is 8 X IO-6M. The pH optimum for enzymatic activity is 7 �4.

AN ISOPHENOXAZINE SYNTHASE FROM PYGNOPORUS COCCINEUS (FR.) BOND. AND SING.

1964 ◽  
Vol 42 (11) ◽  
pp. 1515-1526 ◽  
Author(s):  
P. M. Nair ◽  
L. C. Vining
Keyword(s):  
Electron Acceptor ◽  
Specific Activity ◽  
Fold Increase ◽  
Maximum Activity ◽  
Flavin Mononucleotide ◽  
Temperature Optimum ◽  
Ph Optimum ◽  
Hydroxyanthranilic Acid ◽  
Pycnoporus Coccineus ◽  
Citrate Phosphate

Mycelium from cultures of the red polypore Pycnoporus coccineus (Fr.) Bond. and Sing, contains an enzyme which catalyzes the oxidative condensation of 2 molecules of 2-aminophenol to yield 2-amino-3H-isophenoxazin-3-one. Fractionation of the crude extract has given a preparation with an 893-fold increase in specific activity. The purified enzyme has a pH optimum in citrate-phosphate buffer of 5.0, and a temperature optimum of 55°. The Km value is 4.35 × 10−4 M. FMN and Mn++ ions were required for maximum activity. FAD also served as an electron acceptor. Of the metal ions tested only Mn++ activated the reaction. Hg++ and Fe++ inhibited strongly. The course of the reaction when cofactors were added separately suggested that flavin mononucleotide is the initial electron acceptor and that Mn++ ions are required for reoxidation of the flavin. The enzyme has narrow specificity, and does not catalyze the oxidation of 3-hydroxyanthranilic acid, 3-hydroxykynurenine, or pyrocatechol.

Pyridine–Adenine Dinucleotide Transhydrogenase Activity in Cells Cultured from Rat Hepatoma

1972 ◽  
Vol 50 (5) ◽  
pp. 447-456 ◽  
Author(s):  
C. De Luca ◽  
R. P. Gioeli
Keyword(s):  
Phosphate Buffer ◽  
Pyridine Nucleotide ◽  
Maximum Activity ◽  
Ph Optimum ◽  
Apparent Lack ◽  
Minimal Deviation ◽  
Ph Range ◽  
Pyridine Nucleotide Transhydrogenase ◽  
Rat Hepatoma ◽  
Cells Cultured

Preparations from cells cultured from a minimal-deviation hepatoma in the rat exhibit pyridine nucleotide transhydrogenase (NAD(P)H: NAD(P) oxidoreductase, EC 1.6.1.1) activity. The pH optimum, its release by digitonin, and its apparent lack of dependence on steroids for activity tentatively classify it as a transhydrogenase of the type first described for animal tissue.Enzyme preparations from digitonin-treated homogenates were very unstable. The time necessary for the loss of one-half the activity was 16–18 h when the enzyme was stored at 5 °C; this was reduced to 4 h when storage was in polycarbonate tubes.The enzyme apparently transferred hydrogen directly and with equal ease from NADH to both the 3-acetyl-pyridine and thionicotinamide analogues of NAD. Half-saturation values for NAD and its acetylpyridine analogue were 0.99 × 10−5 M and 3.55 × 10−4 M, respectively. The enzyme exhibited its maximum activity in phosphate buffer at pH 5.8. It was inhibited by 50–60% over the pH range 7.0–8.5 in Tris buffer. This could be reversed by dithiothreitol; reversal was complete between pH 8.0 and 8.5.

scholarly journals Thermostable glucose isomerase from psychrotolerant Streptomyces species

1970 ◽  
Vol 1 ◽  
pp. 6-10 ◽  
Author(s):  
Bidur Dhungel ◽  
Manoj Subedi ◽  
Kiran Babu Tiwari ◽  
Upendra Thapa Shrestha ◽  
Subarna Pokhrel ◽  
...  
Keyword(s):  
Specific Activity ◽  
Fold Increase ◽  
Glucose Isomerase ◽  
Enzyme Concentration ◽  
Maximal Velocity ◽  
Ph Optimum ◽  
Streptomyces Spp ◽  
Optimum Ph ◽  
Optimum Reaction ◽  
Sepharose 4B

Glucose isomerase (EC 5.3.1.5) was extracted from Streptomyces spp., isolated from Mt. Everest soil sample, and purified by ammonium sulfate fractionation and Sepharose-4B chromatography. A 7.1 fold increase in specific activity of the purified enzyme over crude was observed. Using glucose as substrate, the Michaelis constant (KM<) and maximal velocity (Vmax) were found to be 0.45M and 0.18U/mg. respectively. The optimum substrate (glucose) concentration, optimum enzyme concentration, optimum pH, optimum temperature, and optimum reaction time were 0.6M, 62.14μg/100μl, 6.9, 70ºC, and 30 minutes, respectively. Optimum concentrations of Mg2+ and Co2+ were 5mM and 0.5mM, respectively. The enzyme was thermostable with half-life 30 minutes at 100ºC.DOI: 10.3126/ijls.v1i0.2300 Int J Life Sci 1 : 6-10

scholarly journals Gamma Radiolysis of Flavin Mononucleotide and Flavin-Adenine Dinucleotide in Aqueous Solution

1991 ◽  
Vol 64 (8) ◽  
pp. 2532-2538 ◽  
Author(s):  
Abhijit Saha ◽  
Parikshit Chandra Mandal ◽  
Sudhindra Nath Bhattacharyya
Keyword(s):  
Aqueous Solution ◽  
Flavin Adenine Dinucleotide ◽  
Flavin Mononucleotide ◽  
Gamma Radiolysis

scholarly journals 475 Heat Treatments Reduce Irradiation-induced Changes in Phenylpropanoid Metabolism in Grapefruit

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 527A-527
Author(s):  
R.E. McDonald ◽  
W.R. Miller ◽  
T.G. McCollum
Keyword(s):  
Heat Treatment ◽  
Fold Increase ◽  
Heat Treatments ◽  
Maximum Activity ◽  
Phenylpropanoid Metabolism ◽  
Total Phenols ◽  
Citrus Paradisi ◽  
Pal Activity ◽  
Canopy Position ◽  
Induced Changes

Irradiation is being evaluated as a quarantine treatment of grapefruit (Citrus paradisi, Macf.), but it can cause damage to the fruit. We wanted to determine if pre-irradiation heat treatments would improve fruit tolerance to irradiation as they improve tolerance to low-temperature injury. `Marsh' grapefruit were harvested from interior and exterior canopy positions and irradiated at 0 or 1.0 kGy at a dose rate of 0.148 kGy·min-1 before storage for 4 weeks at 10 °C. Following storage, pitting of flavedo tissue was the most evident condition defect noted as a result of irradiation. Pitting was noted on 15% and 27% of irradiated interior and exterior canopy fruit, respectively, whereas there was no pitting on non-irradiated fruit. Temperature conditioning before irradiation decreased the susceptibility of fruit to damage. Pitting was 26%, 19%, and 17% when fruit were held 2 h at 20 (ambient), 38 or 42 °C, respectively. There was a marked increase in phenylalanine ammonia-lyase (PAL) activity following irradiation. Maximum activity (≈18-fold increase) was attained 24 h after irradiation. Irradiation-induced PAL activity was reduced significantly by temperature conditioning at 38 or 42 °C. Exterior canopy fruit flavedo contained higher levels of total phenols, including flavanols and coumarins, compared with interior canopy fruit. The deposition of lignin was not related to canopy position. Neither irradiation nor heat treatment had an effect on total phenols or lignin deposition. It seems that irradiation causes a stress condition in the fruit, which leads to pitting of peel tissue. Heat treatment before irradiation reduced the damaging effects of irradiation.

Enhanced riboflavin incorporation into flavins in newborn riboflavin-deficient rats.

1977 ◽  
Vol 233 (5) ◽  
pp. E397
Author(s):  
C Muttart ◽  
R Chaudhuri ◽  
J Pinto ◽  
R S Rivlin
Keyword(s):  
Subcutaneous Injection ◽  
Flavin Adenine Dinucleotide ◽  
The Other ◽  
Flavin Mononucleotide ◽  
Newborn Rats ◽  
Riboflavin Deficiency ◽  
Riboflavin Deficient ◽  
Covalently Bound

The incorporation of a subcutaneous injection of [14C]riboflavin (2.5 muCi/100 g body wt) into flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and flavins bound covalently to proteins was determined at 1, 6, and 18 h in liver, cerebrum, and cerebellum from progeny of normal and maternally riboflavin-deficient Holtzman rats. Radioactivity remaining as riboflavin was also determined under these circumstances. Experiments were initiated within 24 h of birth. In both groups of newborn rats, the incorporation of radioactive riboflavin into covalently bound flavins in liver and brain proceeded more slowly than into the other flavin fractions. In addition, radioactivity incorporated into covalently bound flavins comprised a relatively smaller proportion of the total amount incorporated in brain than in liver. In progeny of riboflavin-deficient dams, an increased rate of incorporation of riboflavin into all three flavin derivatives, particularly FAD, was observed in liver and brain, compared to results in normal progeny. These data provide evidence that maternal riboflavin deficiency enhances the incorporation of riboflavin into tissue flavins in liver, cerebrum, and cerebellum from newborn rats.

Studies on the enzyme phenol oxidase in a freshwater monogenetic trematode

1986 ◽  
Vol 60 (3) ◽  
pp. 201-209 ◽  
Author(s):  
A. Bhagavathiammai ◽  
K. Ramalingam
Keyword(s):  
Protocatechuic Acid ◽  
Phenol Oxidase ◽  
Maximum Activity ◽  
Ph Optimum ◽  
Cytochemical Localization ◽  
Wide Range

AbstractCytochemical localization of the enzyme phenol oxidase inNeomurraytrema tengrahas been studied. Results reveal that the enzyme reacts with substrates such as catechol, hydroquinone, pyrogallol, dopa, doparmine, epinephrine and tyramine, but not with tyrosine and protocatechuic acid. Thus it shows activity with a wide range of phenols, aminated, mono and diphenols and also with deaminated and decarboxylated, di- and polyphenols. The maximum activity of the enzyme occurs between 40°C and 50°C with a pH optimum of 6–6.

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