scholarly journals The nature of inactivation of rat muscle 5'-adenylate aminohydrolase by fluorodinitrobenzene

1975 ◽  
Vol 145 (2) ◽  
pp. 145-151 ◽  
Author(s):  
A Raggi ◽  
C Bergamini ◽  
G Ronca
Keyword(s):  
Enzyme Activity ◽  
Kinetic Properties ◽  
Hydroxyl Groups ◽  
Amp Deaminase ◽  
Thiol Groups ◽  
Tyrosine Residues ◽  
Nitrobenzoic Acid ◽  
Complete Inactivation ◽  
Lysine Residues ◽  
Phenolic Hydroxyl Groups

1. The inactivation of rat skeletal muscle AMP deaminase by Dnp-F (1-fluoro-2,4-dinitrobenzene) is accompanied by the arylation of thiol, amino and phenolic hydroxyl groups. 2. The number of thiol groups that react with Dnp-F is about 12; this is the number that reacts with Nbs2 [5,5′-dithiobis-(2-nitrobenzoic acid)] and N-ethylmaleimide without loss of enzyme activity, and it appears to be the same thiol groups that all three reagents attack. 3. Dinitrophenylation of these reactive SH groups is not the cause of inactivation, since active N-ethylmaleimide-substituted enzyme is also inactivated by Dnp-F.4. Complete inactivation of the N-ethylmaleimide-treated AMP deaminase occurs when about six tyrosine and two lysine residues are dinitrophenylated. 5. Since the treatment of Dnp-enzyme with 2-mercaptoethanol restores much of the enzyme activity, inactivation of AMP deaminase by Dnp-F is probably largely due to modification of tyrosine residues. 6. The kinetic properties of the Dnp-enzyme indicate that a marked decrease in V occurs only after extensive enzyme modification. The decreased activity after slight inactivation results from modification of Km.

scholarly journals Inactivation of rat muscle 5′-adenylate aminohydrolase by tyrosine nitration with tetranitromethane

1981 ◽  
Vol 193 (3) ◽  
pp. 853-859
Author(s):  
M Ranieri-Raggi ◽  
C Bergamini ◽  
U Montali ◽  
A Raggi
Keyword(s):  
Enzyme Activity ◽  
Kinetic Properties ◽  
Tyrosine Nitration ◽  
Amp Deaminase ◽  
Thiol Groups ◽  
Rapid Loss ◽  
Binding Properties ◽  
Tyrosine Residues ◽  
Rat Muscle ◽  
Molar Excess

Reaction of rat muscle AMP deaminase with low molar excess of tetranitromethane results in a rapid loss of free thiol groups and a concomitant decrease in enzyme activity at high, but not at low, AMP concentration. This modification appears to be limited to the same non-essential thiol groups reactive towards specific reagents in non-denaturing conditions. On incubation with higher molar excess of tetranitromethane, a loss of enzyme activity is observed, which correlates with nitration of tyrosine residues. By amino acid analysis, approximately there tyrosine residues per subunit are estimated to be nitrated in the completely inactivated enzyme. The kinetic properties of the partially inactivated AMP deaminase reveal a negative co-operatively behaviour at approximately half saturation. This suggests that modification of tyrosine residues is also responsible for alteration of the binding properties of the hypothesized activating site of AMP deaminase.

scholarly journals Phospholipase C from Bacillus cereus. Evidence for essential lysine residues

1977 ◽  
Vol 161 (1) ◽  
pp. 159-165 ◽  
Author(s):  
B Aurebekk ◽  
C Little
Keyword(s):  
Enzyme Activity ◽  
Phospholipase C ◽  
Specific Activity ◽  
Schiff’S Base ◽  
Absorbance Maximum ◽  
Complete Inactivation ◽  
Lysine Residues ◽  
Essential Lysine Residues ◽  
Base Formation ◽  
Fluorescent Component

1. Phospholipase C was inactivated by exposure to the three amino-group reagents, ethyl acetamidate, 2,4,6-trinitrobenzensulphonic acid and pyridoxal 5′-phosphate plus reduction. 2. Inactivation by pyridoxal 5′-phosphate showed the characteristics of Schiff's base formation with the enzyme. The pyridoxal 5′-phosphate-treated enzyme after reduction had an absorbance maximum at 325 mm and 6-N-pyridoxyl-lysine was the only fluorescent component after acid hydrolysis. 3. For complete inactivation, 2 mol of pyridoxal 5′-phosphate or 7 mol of 2,4,6-trinitrophenyl were incorporated/mol of enzyme. 4. The two apparently essential lysine residues were much more reactive to pyridoxal 5′-phosphate than the other 19 lysine residues in the enzyme. 5. Binding of phospholipase C to a substrate-based affinity gel caused marked protection against inactivation by pyridoxal 5′-phosphate. For complete inactivation of the gel-bound enzyme, 5 mol of pyridoxal 5′-phosphate were incorporated/mol of enzyme and there was no evidence of two especially reactive lysine residues. 6. On application of pyridoxal 5′-phosphate-treated enzyme (remaining activity 30% of original) to a column of the affinity gel, some material bound and some did not. The latter contained very little enzyme activity and was heavily incorporated with reagent (9.06 mol/mol of enzyme). The former had a specific activity of 34% of that of the control and contained 1.29 mol of reagent/mol of enzyme. 7. Thus phospholipase C appears to contain two lysine residues that are essential for enzyme activity, but probably not for substrate binding.

scholarly journals The regulation of rat liver xanthine oxidase. Involvement of thiol groups in the conversion of the enzyme activity from dehydrogenase (type D) into oxidase (type O) and purification of the enzyme

1972 ◽  
Vol 126 (3) ◽  
pp. 739-745 ◽  
Author(s):  
E D Corte ◽  
F. Stirpe
Keyword(s):  
Enzyme Activity ◽  
Xanthine Oxidase ◽  
Rat Liver ◽  
Copper Sulphate ◽  
Liver Homogenate ◽  
Nitrobenzoic Acid ◽  
Complete Inactivation ◽  
Type D ◽  
Pigeon Liver ◽  
Lung And Kidney

1. The ‘xanthine oxidase’ activity of rat liver supernatant, most of which behaves as an NAD+-dependent dehydrogenase (type D) can be rapidly converted into an oxidase (type O) by thiol reagents such as tetraethylthiuram disulphide, copper sulphate, 5,5′-dithiobis-(2-nitrobenzoic acid), N-ethylmaleimide and p-hydroxymercuribenzoate. Treatment with copper sulphate, if prolonged, leads to almost complete inactivation of the enzyme. The effect of these reagents is prevented by dithioerythritol, and in all cases but that of N-ethylmaleimide is reversed by the same thiol. 2. Dithioerythritol prevents and reverses the conversion of xanthine oxidase from type D into type O brought about by storage of rat liver supernatant at -20°C, preincubation under anaerobic conditions, treatment with carbon or with diethyl ether, and reverses, but does not prevent, the conversion obtained by preincubation of the whole liver homogenate. 3. Conversion of the enzyme from type D into type O is effected by preincubation of rat liver supernatant with the sedimentable fraction from rat liver but not from chick or pigeon liver. The xanthine dehydrogenase activity of chick liver supernatant is not changed into an oxidase by preincubation with the sedimentable fraction from rat liver. 4. The enzyme activity of rat liver supernatant is converted from type D into type O during purification of the enzyme: the purified enzyme can be reconverted into type D by dithioerythritol. 5. The enzyme appears as an oxidase in the supernatant of rat heart, intestine, spleen, pancreas, lung and kidney. The enzyme of all organs but intestine can be converted into a dehydrogenase by dithioerythritol.

scholarly journals Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2131
Author(s):  
Leonardo Dalseno Antonino ◽  
Júlia Rocha Gouveia ◽  
Rogério Ramos de Sousa Júnior ◽  
Guilherme Elias Saltarelli Garcia ◽  
Luara Carneiro Gobbo ◽  
...  
Keyword(s):  
Experimental Work ◽  
Chemical Structure ◽  
31P Nmr ◽  
Kraft Lignin ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Diphenylmethane Diisocyanate ◽  
Complex Chemical ◽  
Heterogeneous Reactivity ◽  
Phenolic Hydroxyl Groups

Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.

Genetic and other determinants of AMP deaminase activity in healthy adult skeletal muscle

1998 ◽  
Vol 85 (4) ◽  
pp. 1273-1278 ◽  
Author(s):  
Barbara Norman ◽  
Donna K. Mahnke-Zizelman ◽  
Amy Vallis ◽  
Richard L. Sabina
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Activity ◽  
Mutant Allele ◽  
Fiber Type ◽  
Type I ◽  
Training Status ◽  
Amp Deaminase ◽  
Normal Allele ◽  
Relative Percentage ◽  
Type I Fibers

AMPD1 genotype, relative fiber type composition, training status, and gender were evaluated as contributing factors to the reported variation in AMP deaminase enzyme activity in healthy skeletal muscle. Multifactorial correlative analyses demonstrate that AMPD1 genotype has the greatest effect on enzyme activity. An AMPD1 mutant allele frequency of 13.7 and a 1.7% incidence of enzyme deficiency was found across 175 healthy subjects. Homozygotes for the AMPD1 normal allele have high enzyme activities, and heterozygotes display intermediate activities. When examined according to genotype, other factors were found to affect variability as follows: AMP deaminase activity in homozygotes for the normal allele exhibits a negative correlation with the relative percentage of type I fibers and training status. Conversely, residual AMP deaminase activity in homozygotes for the mutant allele displays a positive correlation with the relative percentage of type I fibers. Opposing correlations in different homozygous AMPD1 genotypes are likely due to relative fiber-type differences in the expression of AMPD1 and AMPD3 isoforms. Gender also contributes to variation in total skeletal muscle AMP deaminase activity, with normal homozygous and heterozygous women showing only 85–88% of the levels observed in genotype-matched men.

scholarly journals Kinetic properties of AMP deaminase in acute experimental pancreatitis.

1994 ◽  
Vol 41 (2) ◽  
pp. 158-160
Author(s):  
E Kossowska ◽  
J Purzycka-Preis ◽  
M Woźniak ◽  
M Zydowo ◽  
Z Sledźiński
Keyword(s):  
Experimental Pancreatitis ◽  
Kinetic Properties ◽  
Amp Deaminase ◽  
Acute Experimental Pancreatitis
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