scholarly journals The effect of substrate concentration and pH on the enzymic sulphation of l-tyrosyl derivatives

1970 ◽  
Vol 116 (5) ◽  
pp. 805-810 ◽  
Author(s):  
P. Mattock ◽  
D. J. Barford ◽  
J. M. Basford ◽  
J. G. Jones
Keyword(s):  
Methyl Ester ◽  
Enzyme Preparation ◽  
The Other ◽  
Hydroxyl Group ◽  
Amino Group ◽  
Group 4 ◽  
Km Value ◽  
Rapid Equilibrium ◽  
Kinetics Of ◽  
Derivatives Of

1. The kinetics of the enzymic transfer of sulphate from adenosine 3′-phosphate 5′[35S]-sulphatophosphate to derivatives of l-tyrosine were investigated with a partially purified enzyme preparation from rat liver. 2. At pH7.5 and 37°C the Km values for l-tyrosine methyl ester and adenosine 3′-phosphate 5′[35S]-sulphatophosphate are 0.3mm and 8nm respectively. The Km value for either substrate is independent of the concentration of the other. The available data are consistent with the sulphation reaction proceeding according to a rapid-equilibrium random Bi Bi mechanism. 3. From the effect of pH on the Km and Vmax. values for l-tyrosine methyl ester, tyramine and N-acetyl-l-tyrosine ethyl ester it is concluded that the enzyme is specific for substrate molecules with a free and unprotonated amino group and an un-ionized hydroxyl group. 4. The only ionizing group that can be positively attributed to the enzyme appears to influence the binding of adenosine 3′-phosphate 5′[35S]-sulphatophosphate and has an apparent pK value of approx. 9.5. It is suggested that this group may be an essential thiol. 5. The enzyme is inhibited by iodoacetamide at pH7.5 and 30°C and this inhibition is prevented by the presence of adenosine 3′-phosphate 5′[35S]-sulphatophosphate but not by l-tyrosine methyl ester.

THE KINETICS OF AMINO GROUP TRANSFER BY CORN RADICLE TRANSAMINASE

1957 ◽  
Vol 35 (12) ◽  
pp. 1289-1303 ◽  
Author(s):  
F. S. Cook
Keyword(s):  
Classical Theory ◽  
Spectrophotometric Method ◽  
Substrate Concentration ◽  
Enzyme Preparation ◽  
Reaction Rate ◽  
Amino Group ◽  
Group Transfer ◽  
Kinetics Of ◽  
Published Account

The kinetics of transamination are complicated by the presence of two substrates whose concentrations change appreciably during the course of the reaction. The only previously published account of the kinetics of this system deviates considerably from classical theory. Equations based on premises of Michaelis and Menten have been shown, however, to accommodate the data on reaction rate in relation to substrate concentration obtained with a corn radicle enzyme preparation by a spectrophotometric method.

Partial hydrolysis of acyl 1,6-anhydro-β-D-glucopyranose

1984 ◽  
Vol 49 (8) ◽  
pp. 1780-1787 ◽  
Author(s):  
Štefan Kučár ◽  
Juraj Zámocký ◽  
Juraj Zemek ◽  
Dušan Anderle ◽  
Mária Matulová
Keyword(s):  
Acid Hydrolysis ◽  
Hydrazine Hydrate ◽  
Hydrogen Chloride ◽  
Ester Group ◽  
The Other ◽  
Hydroxyl Group ◽  
Partial Hydrolysis ◽  
Substantial Influence ◽  
Hydrolysis Of ◽  
Derivatives Of

Partial hydrolysis of per-O-acetyl- and per-O-benzoyl derivatives of 1,6-anhydro-β-D-glucopyranose with methanolic hydrogen chloride and hydrazine hydrate was investigated. The acyl group at C(3) is of substantial influence on the course of hydrolysis. The esterified hydroxyl group at C(3) was found to be most stable on acid hydrolysis with methanolic hydrogen chloride when compared with that at C(2), or C(4); on the other hand, this ester group is the most labile upon hydrolysis with hydrazine hydrate. Selectivity of the respective ester groups towards hydrolysis made it possible to prepare all variations of acetyl and benzoyl derivatives of 1,6-anhydro-β-D-glucopyranose.

scholarly journals Comparative studies on the 25-hydroxylations of cholecalciferol and 1α-hydroxycholecalciferol in perfused rat liver

1978 ◽  
Vol 170 (3) ◽  
pp. 495-502 ◽  
Author(s):  
Masafumi Fukushima ◽  
Yasuho Nishii ◽  
Michiko Suzuki ◽  
Tatsuo Suda
Keyword(s):  
Vitamin D ◽  
Rat Liver ◽  
Linear Relation ◽  
Comparative Studies ◽  
Similar Rate ◽  
The Other ◽  
Perfused Rat Liver ◽  
Km Value ◽  
Derivatives Of ◽  
25 Hydroxycholecalciferol

The 25-hydroxylations of [3H]cholecalciferol and 1α-hydroxy[3H]cholecalciferol in perfused rat liver were compared. Results showed that about twice as much 1α(OH)D3 (1α-hydroxycholecalciferol) was incorporated into the liver as cholecalciferol. 25-Hydroxy[3H]cholecalciferol and 1α-25-dihydroxy[3H]cholecalciferol were not incorporated significantly. Livers isolated from vitamin D-deficient rats formed the 25-hydroxy derivatives of cholecalciferol and 1α(OH)D3 respectively linearly with time for at least 120min. The rate of 1α,25(OH)2D3 (1α,25-dihydroxycholecalciferol) production increased exactly 10-fold on successive 10-fold increases in the dose of 1α(OH)D3, suggesting that hepatic 25-hydroxylation of 1α(OH)D3 is not under metabolic control. On the other hand, the rate of conversion of cholecalciferol into 25(OH)D3 (25-hydroxycholecalciferol) did not increase linearly with increase in the amount of cholecalciferol in the perfusate. The 25-hydroxylation of cholecalciferol seemed to proceed at a similar rate to that of 1α(OH)D3 at doses of less than 1nmol, but with doses of more than 2.5nmol, the conversion of cholecalciferol into 25(OH)D3 became much less efficient, though the linear relation between the amounts of substrate and product was maintained. A reciprocal plot of data on the 25-hydroxylation of cholecalciferol gave two Km values of about 5.6nm and 1.0μm, whereas that for the 25-hydroxylation of 1α(OH)D3 gave a single Km value of about 2.0μm. These results suggest that there are two modes of 25-hydroxylation of cholecalciferol in the liver, which seem to be closely related to the mechanism of control of 25(OH)D3 production by the liver.

scholarly journals Antioxidant activity of some coumarins / Antioxidačná activita niektorých kumarínov

2015 ◽  
Vol 62 (s9) ◽  
pp. 41-45 ◽  
Author(s):  
F. Šeršeň ◽  
M. Lácová
Keyword(s):  
Antioxidant Activity ◽  
Acetic Acid ◽  
Superoxide Anion ◽  
The Other ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Coumarin Derivatives ◽  
Antioxidant Effectiveness ◽  
Derivatives Of ◽  
Superoxide Anion Radicals

AbstractNineteen derivatives of coumarin were tested on the scavenging of 2,2-diphenyl-1-picrylhydrazyl, hydroxyl and superoxide anion radicals. It was found that antioxidant activity exhibits only such coumarins that contain hydroxyl groups. The derivatives without hydroxyl group showed very low antioxidant effectiveness or they were ineffective. On the other hand, the greatest antioxidant effectiveness was exhibited by coumarin derivatives that contained hydroxyl groups in 6 or 8 position, whereas the effectiveness of derivatives with one hydroxyl group in 4, 5 or 7 position was very low. Based on scavenging of the above-mentioned radicals, it was found that the most effective scavengers were 7,8-dihydroxy-4-methylcoumarin (i.e. compound that contains two hydroxyl groups in 7 and 8 positions), (7,8-dihydroxy-2-oxo-2H-chromen-4-yl)acetic acid (this compound contains in addition to two hydroxyl groups in 7 and 8 positions also one hydroxyl group in the acidic residue), esculetin (6,7-dihydroxycoumarin) and 6,7-dihydroxy-4-methylcoumarin.

Acid-catalyzed migration of N4-acyl groups in cytosine derivatives

1979 ◽  
Vol 44 (6) ◽  
pp. 1819-1827 ◽  
Author(s):  
Antonín Holý
Keyword(s):  
Acetic Acid ◽  
Trifluoroacetic Acid ◽  
The Other ◽  
Aqueous Acetic Acid ◽  
Amino Group ◽  
Benzoyl Group ◽  
Benzoyl Cyanide ◽  
Acid Catalyzed ◽  
Derivatives Of ◽  
Anhydrous Acetic Acid

Heating 1-(2,3-di-O-benzoyl-β-D-arabinofuranosyl)-N4-benzoylcytosine (I) in 80% acetic acid afforded 1-(2,3-di-O-benzoyl-β-D-arabinofuranosyl)-N3-benzoylcytosine (II). Benzoylation of 5'-O-tritylcytidine (V) led to the 2',3',N4-tribenzoyl derivative VI which was refluxed with 80% acetic acid to give 2',3',N3-tribenzoylcytidine (VII). Analogously, 2',3',5',N4-tetrabenzoylcytidine (IX), prepared by benzoylation of cytidine with benzoyl cyanide, gave on reflux with 80% acetic acid 2',3',5',N3-tetrabenzoylcytidine (X). Under identical conditions, 1-methyl-N4-benzoylcytosine (XI) afforded directly 1-methyluracil (XII) .This migration takes place also in acetyl derivatives of cytosine nucleosides: 2',3',5',N4-tetraacetylcytidine (XIII) was transformed to the N3-acetylcytosine derivative XIV. On the other hand, migration of acetyl or benzoyl group from the exo-amino group of adenine has not been observed under the mentioned conditions. The migration of the N4-acyl group of cytosine derivatives proceeds best in aqueous acetic acid, more slowly also in anhydrous acetic acid, but not by action of trifluoroacetic acid in 1,2-dichloroethane.

scholarly journals Purification from rat liver of an enzyme that catalyses the sulphurylation of phenols

1971 ◽  
Vol 123 (5) ◽  
pp. 901-906 ◽  
Author(s):  
F. A. McEvoy ◽  
J. Carroll
Keyword(s):  
Enzyme Activity ◽  
Methyl Ester ◽  
Rat Liver ◽  
The Other ◽  
Male Rat ◽  
Thiol Compounds ◽  
Km Value ◽  
Rat Livers

1. An enzyme (EC 2.8.2.1) that catalyses the transfer of sulphate from adenosine 3′-phosphate 5′-sulphatophosphate to phenols was purified approx. 2000-fold from male rat livers. 2. The purified preparation did not catalyse the sulphurylation of dehydroepiandrosterone, butan-1-ol, l-tyrosine methyl ester, 1-naphthylamine or serotonin. 3. At pH8.0 and 37°C the Km values of the enzyme for p-nitrophenol and adenosine 3′-phosphate 5′-sulphatophosphate are 51 and 14μm respectively. The Km value for either substrate is independent of the concentration of the other. 4. The sulphurylation of phenol is inhibited by thiol compounds and glutathione at a concentration of 3mm caused an approx. 50% decrease in enzyme activity. 5. The Km of the enzyme for adenosine 3′-phosphate 5′-sulphatophosphate is unaffected by the presence of added glutathione but at a concentration of 5mm-glutathione the Km of the enzyme for its phenolic substrate is decreased.

scholarly journals Chemical and metabolic properties of adenosine diphosphate ribose derivatives of nuclear proteins.

1975 ◽  
Vol 147 (3) ◽  
pp. 523-529 ◽  
Author(s):  
J A Smith ◽  
L A Stocken
Keyword(s):  
Adenosine Diphosphate ◽  
S Phase ◽  
The Other ◽  
Hydroxyl Group ◽  
Small Peptide ◽  
Histone 3 ◽  
Liver Nuclei ◽  
Metabolic Properties ◽  
Derivatives Of ◽  
Covalently Bound

1. ADP-ribose is found in rat liver nuclei covalently bound to histone F1, to a non-histone protein, and to a small peptide. 2. A single unit of ADP-ribose, covalently bound to phosphoserine, was isolated from an enzymic hydrolysate of histone F1. ADP-ribose-bearing peptides were isolated from a tryptic digest of the histone. 3. It is proposed that the 1′-hydroxyl group of ADP-ribose is linked to the phosphate group of phosphoserine in histone F1. 4. The incorporation of 32P into ADP-ribose on histone F1 a parallels the DNA content through the cell cycle. An increased incorporation of the nucleotide into the other derivatives is observed during S phase. 5. It is suggested that the ADP-ribose derivative of histone F1 has a role in maintaining the G0 state and that one or both of the other derivatives is concerned with control of DNA synthesis.

scholarly journals Kinetics and mechanism of catalysis by proteolytic enzymes. A comparison of the kinetics of hydrolysis of synthetic substrates by bovine α- and β-trypsin

1974 ◽  
Vol 141 (2) ◽  
pp. 545-554 ◽  
Author(s):  
D. V. Roberts ◽  
D. T. Elmore
Keyword(s):  
Methyl Ester ◽  
Proteolytic Enzymes ◽  
Catalytic Efficiency ◽  
Kinetics And Mechanism ◽  
Molecular Flexibility ◽  
Kinetics Of Hydrolysis ◽  
Mechanism Of Catalysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Several esters of the α-N-toluene-p-sulphonyl and α-N-benzoyl derivatives of S-(3-aminopropyl)-l-cysteine and the methyl ester of S-(4-aminobutyl)-N-toluene-p-sulphonyl-l-cysteine were synthesized. The kinetics of hydrolysis of these and esters of the α-N-toluene-p-sulphonyl and α-N-benzoyl derivatives of l-arginine, l-lysine, S-(2-aminoethyl)-l-cysteine and esters of γ-guanidino-l-α-toluene-p-sulphonamidobutyric acid and α-N-toluene-p-sulphonyl-l-homoarginine by α- and β-trypsin were compared. On the basis of values of the specificity constants (kcat./Km), the two enzymes display similar catalytic efficiency towards some substrates. In other cases α-trypsin is less efficient than β-trypsin. It is possible that α-trypsin possesses greater molecular flexibility than β-trypsin.

scholarly journals Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

2020 ◽  
Author(s):  
Emine Salamci ◽  
Yunus Zozik
Keyword(s):  
The Other ◽  
Hydroxyl Group ◽  
Efficient Synthesis ◽  
Azide Group ◽  
Methanol Treatment ◽  
Stereoselective Syntheses ◽  
Hydrolysis Of ◽  
Derivatives Of

The efficient synthesis of two new stereoisomeric 3-aminocyclooctanetriols and new halocyclitol derivatives of them starting from cis,cis-1,3-cyclooctadiene are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxyl group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to the corresponding cyclic sulphate via the formation of a cyclic sulphite in the presence of catalytic RuO4. Reaction of this cyclic sulphate with a nucleophilic azide followed by the reduction of the azide group provided the target, 3-aminocyclooctanetriol. The second key compound, bromotriol, was prepared by epoxidation of the cyclooctene diol with m-chloroperbenzoic acid followed by hydrolysis with HBr(g) in methanol. Treatment of bromotriol with NaN3 and the reduction of the azide group yielded the other 3-aminocyclooctanetriol desired. Hydrolysis of the epoxides with HCl(g) in methanol gave stereospecifically new chlorocyclooctanetriols.

THE KINETICS OF AMINO GROUP TRANSFER BY CORN RADICLE TRANSAMINASE

1957 ◽  
Vol 35 (1) ◽  
pp. 1289-1303 ◽  
Author(s):  
F. S. Cook
Keyword(s):  
Classical Theory ◽  
Spectrophotometric Method ◽  
Substrate Concentration ◽  
Enzyme Preparation ◽  
Reaction Rate ◽  
Amino Group ◽  
Group Transfer ◽  
Kinetics Of ◽  
Published Account

The kinetics of transamination are complicated by the presence of two substrates whose concentrations change appreciably during the course of the reaction. The only previously published account of the kinetics of this system deviates considerably from classical theory. Equations based on premises of Michaelis and Menten have been shown, however, to accommodate the data on reaction rate in relation to substrate concentration obtained with a corn radicle enzyme preparation by a spectrophotometric method.

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