scholarly journals The mechanism of action of β-glucosidase from Botryodiplodia theobromae Pat

1987 ◽  
Vol 241 (2) ◽  
pp. 455-462 ◽  
Author(s):  
G M Umezurike
Keyword(s):  
Mechanism Of Action ◽  
Rate Equation ◽  
Enzymic Activity ◽  
Botryodiplodia Theobromae ◽  
Acidic Group ◽  
Linear Decrease ◽  
Low Concentrations ◽  
Acetic Acid Buffer ◽  
Beta Glucosidase ◽  
Enzyme Intermediate

The activity of the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) obtained from culture filtrates of Botryodiplodia theobromae Pat. was affected by added NaCl in such a way that an initial phase of stimulation was followed by a phase of rapid non-linear decrease in velocity and finally by a phase of slow linear decrease in velocity as the concentration of NaCl was increased. In the presence of 0.014 M-sodium acetate/acetic acid buffer (pH 5.0) there was a slight increase in enzymic activity in the presence of low concentrations of dioxan (up to about 10% dioxan) and a rapid decrease in enzymic activity at higher dioxan concentrations, but both effects were mitigated in the presence of 0.1 M buffer. The order of efficiency of added glucosyl acceptors in beta-glucosidase-catalysed reactions was found to be fructose greater than sucrose greater than glycerol greater than methanol. The enzyme was inactivated by the active-site-directed compound conduritol-B-epoxide; but this inactivation was concentration-dependent, was prevented by 10 mM-glucose, and involved an acidic group with pKa 4.3. A rate equation has been derived on the assumption of a mechanism of action involving a solvent-separated and an intimate glucosyl cation-carboxylate ion-pair intermediate and an alpha-glucosyl enzyme intermediate [Umezurike, G. M. (1981) Biochem. J. 199, 203-209]. Calculations based on the application of the derived rate equation and the calculated kinetic parameters show that the rate equation explains the peculiar properties of beta-glucosidase in the presence of added glucosyl acceptors or of NaCl.

scholarly journals The β-glucosidase from Botryodiplodia theobromae. Mechanism of enzyme-catalysed reactions

1979 ◽  
Vol 179 (3) ◽  
pp. 503-507 ◽  
Author(s):  
G M Umezurike
Keyword(s):  
Maximum Velocity ◽  
Enzymic Activity ◽  
Enzyme Mechanism ◽  
Botryodiplodia Theobromae ◽  
Imidazole Group ◽  
Group 4 ◽  
Effects Of Ph ◽  
Group 3 ◽  
High Concentrations ◽  
Beta Glucosidase

The effects of pH and temperature on Michaelis constant (Km) and maximum velocity (Vmax.) and of NaCl on the activity of the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase EC 3.2.1.21) from cultures of Botryodiplodia theobromae Pat. have been studied. 2. Donor binding and inhibition of activity by glucose were dependent on the ionization of a group (pK 6.0) that appeared to be an imidazole group. 3. Catalytic activity and the stimulation of activity by glycerol were dependent on the ionization of two groups, which appeared to be a carboxy group and an imidazole group. 4. The Arrhenius activation energy (Ea) calculated from results obtained at pH 4.0 and 5.0 was about 45–46kJ.mol-1. 5. The enthalpies (delta H0) calculated from results obtained at pH 4.0 and 5.0 were similar (about -4kJ.mol-1), whereas at pH 6.5 the value was about -33kJ.mol-1. 6. The entropies (delta S0) calculated from these results at 37 degrees C were -21, -22 and -118J.K-1.mol-1 at pH 4.0, 5.0 and 6.5 respectively. A low concentration of NaCl (16.6 mM) stimulated enzymic activity and decreased the Km for the donor, whereas high concentrations (up to 500 mM) inhibited enzymic activity, increased the Km and had no effect on Vmax. 8. Plots of initial velocity data obtained in the presence of dioxan as 1/v against the ratio of the molar concentration of dioxan to that of water were linear. 9. The results are discussed in terms of the enzyme mechanism.

The structure and mechanism of action of papain

1970 ◽  
Vol 257 (813) ◽  
pp. 237-248 ◽  
Keyword(s):  
Mechanism Of Action ◽  
Catalytic Mechanism ◽  
Proteolytic Enzymes ◽  
Cysteine Proteinase ◽  
Preceding Paper ◽  
Cysteine Residue ◽  
Enzymic Activity ◽  
Critical Survey ◽  
Cysteine Proteinases ◽  
Stem Bromelain

The cysteine proteinases form a group of enzymes which depend for their enzymic activity on the thiol group of a cysteine residue. Several which occur in plants have been investigated extensively and include papain, ficin and stem bromelain (Smith & Kimmel i960). Although the term papain, introduced last century to describe the proteolytic principle in papaya latex (Wurtz & Bouchut 1879) is still used to describe crude dried latex, the crystalline enzyme is readily obtained (Kimmel & Smith 1954). Ficin is known to consist of several closely related enzymes which have been resolved (Sgarbieri, Gupte, Kramer & Whitaker 1964), but for most structural and mechanistic studies the unresolved mixture of enzymes has been used. Stem bromelain also appears to be a mixture of at least two proteolytic enzymes which have not yet been resolved (Ota, Moore & Stein 1962; Murachi 1964). In spite of the recognized heterogeneity of ficin and stem bromelain, it does seem that both structurally and mechanistically they are similar to papain. Only one bacterial cysteine proteinase has received a detailed study, namely, streptococcal proteinase, and it appears to have little or no relation in its amino acid sequence with the plant enzymes (Liu, Stein, Moore & Elliott 1965). The functional groups involved in the catalytic mechanism are apparently the same as in the plant proteinases (Gerwin, Stein & Moore 1966; Liu 1967; Husain & Lowe 1968 a , c ), but the mechanism of action has not been extensively studied. It may well be however that the plant and bacterial cysteine proteinases have converged onto a similar mechanism of action by two independent evolutionary pathways, as now seems apparent for the animal and bacterial serine proteinases (Alden, Wright & Kraut, this volume, p. 119). Because the tertiary crystal structure of papain (Drenth, Jansonius, Koekoek, Swen & Wolthers 1968; see also the preceding paper, p. 231) is now known, a critical survey of this enzyme is apposite.

scholarly journals The action on cellulose and its derivatives of a purified 1,4-β-glucanase from Trichoderma koningii

1981 ◽  
Vol 199 (2) ◽  
pp. 409-417 ◽  
Author(s):  
G Halliwell ◽  
R Vincent
Keyword(s):  
Specific Activity ◽  
High Specificity ◽  
Enzymic Activity ◽  
Transferase Activity ◽  
Beta Glucanase ◽  
Trichoderma Koningii ◽  
Initial Substrate ◽  
Central Bond ◽  
Beta Glucosidase ◽  
Derivatives Of

The specific properties have been examined of the 1,4-beta-glucanase component of Trichoderma koningii that participates in an early and effective stage of random breakdown of native cellulose to short fibres. The enzyme was purified and freed from associated components of the cellulase complex (particularly beta-glucosidase) that interfere with, and complicate interpretation of, the action of such enzymes. Purification increased the specific activity 25-fold over culture filtrates; the enzyme hydrolysed CM-cellulose faster than the purified beta-glucosidase from the same organism hydrolysed any of its substrates (cellobiose or cellodextrins). The specificity of the glucanase was directed towards soluble derivatives of cellulose, CM-cellulose and cellodextrins, and not to insoluble cellulose or alpha-linked polymers. The approximate Km was 2.5 mg of CM-cellulose . ml-1 at 37 degrees C at the optimum pH, 5.5, where enzymic activity was maximal with 6--7 mg of CM-cellulose . ml-1 and inhibited by higher concentrations. The temperature optimum was 60 degrees C. The glucanase attacked larger cellodextrins (cellohexaose to cellotetraose, in that order) much more readily than smaller dextrins (cellobiose and cellotriose) and released a mixture of products, glucose up to cellopentaose, which was quantitatively determined after chromatography on charcoal. Similar examination of hydrolysates of the reduced cellodextrins showed clearly the high specificity of the enzyme for the central bond of its natural substrates (the cellodextrins), whatever their chain length, and indicated the nature of the enzyme as an endoglucanase. Outer bonds shared a weaker, but similar, susceptibility to enzymic cleavage. Transferase activity was absent and no larger dextrins than the initial substrate were formed.

scholarly journals The mechanism of folding of globular proteins. Suitability of a penicillinase from Staphylococcus Aureus as a model for refolding studies

1976 ◽  
Vol 155 (2) ◽  
pp. 325-330 ◽  
Author(s):  
B Robson ◽  
R H. Pain
Keyword(s):  
Staphylococcus Aureus ◽  
Enzymic Activity ◽  
Optical Rotatory Dispersion ◽  
Native Conformation ◽  
Guanidinium Chloride ◽  
Tyrosine Residues ◽  
Low Concentrations ◽  
Unfolded State ◽  
Solvent Molecules ◽  
Homogeneous Preparation

1. A homogeneous preparation of penicillinase (penicillin amido-β-lactamhydrolase, EC 3.5.2.6) was isolated and purified from cultures of Staphylococcus aureus by a simple two-stage procedure. 2. The native protein contains 20-30% helix as determined by optical-rotatory-dispersion and circular-dichroism measurements. Some 54(+/-5)% of the 13 tyrosine residues are exposed to solvent molecules of diameter 0.44 and 0.94 nm. 3. Conditions that allow full recovery of enzymic activity and native conformation from the fully unfolded state in 4M-guanidinium chloride were defined. 4. Refolding of the protein was shown to be inhibited by intermolecular interaction, by small changes in ionization and by low concentrations (0.025 M) of phenol.

scholarly journals Hydrolysis of dietary flavonoid glycosides by strains of intestinal Bacteroides from humans

1987 ◽  
Vol 248 (3) ◽  
pp. 953-956 ◽  
Author(s):  
V D Bokkenheuser ◽  
C H Shackleton ◽  
J Winter
Keyword(s):  
Healthy Subjects ◽  
Enzymic Activity ◽  
Flavonoid Glycosides ◽  
Faecal Flora ◽  
A Cell ◽  
Bacteroides Ovatus ◽  
Dietary Flavonoid ◽  
Beta Glucosidase ◽  
Hydrolysis Of ◽  
Beta Galactosidase

Rutin and quercitrin are hydrolysed to quercetin, and robinin is hydrolysed to kaempferol, by faecal flora from healthy subjects. The enzymes required for these hydrolyses, namely alpha-rhamnosidase and beta-galactosidase, were produced by some strains of Bacteroides distasonis; other strains, however, synthesized beta-glucosidase. The last-named enzyme was also elaborated by Bacteroides uniformis and Bacteroides ovatus. All the enzymes were produced constitutively. A cell-free extract of B. distasonis containing beta-glucosidase displayed an enzymic activity of 1 mumol/10 min per 10 mg of protein.

scholarly journals The active site of β-glucosidase from Botryodiplodia theobromae. Effects of pH and dioxan on enzyme-catalysed reactions

1977 ◽  
Vol 167 (3) ◽  
pp. 831-833 ◽  
Author(s):  
G M Umezurike
Keyword(s):  
Molecular Weight ◽  
Active Site ◽  
Maximum Velocity ◽  
Carboxyl Group ◽  
Michaelis Constant ◽  
Botryodiplodia Theobromae ◽  
Effects Of Ph ◽  
Group 2 ◽  
Beta Glucosidase ◽  
Hydrolysis Of

1. The hydrolysis of o-nitrophenyl beta-D-glucopyranoside by the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) of Botryodiplodia theobromae Pat in the absence or presence of added dioxan was found to be dependent on the ionization of two groups, which appeared to be a carboxyl group and an imidazole group. 2. Dioxan increased the Michaelis constant, Km, but decreased the maximum velocity, V.

Influence of the Safener Benoxacor on the Metabolism of Metolachlor in Corn

1991 ◽  
Vol 46 (9-10) ◽  
pp. 846-849 ◽  
Author(s):  
C. K. Cottingham ◽  
K. K. Hatzios
Keyword(s):  
Mechanism Of Action ◽  
Dose Response ◽  
Similar Degree ◽  
Glutathione S Transferase ◽  
Corn Hybrids ◽  
Polar Metabolite ◽  
Herbicide Safener ◽  
Low Concentrations ◽  
Gst Activity ◽  
Corn Hybrid

Abstract The herbicide safener benoxacor (CGA -154281) is effective in protecting corn from meto­lachlor injury. Glutathione-S-transferase (GST) activity of corn seedlings was stimulated by low concentrations of benoxacor as was the formation of a polar metabolite identified as the glutathione (GSH) conjugate of metolachlor. A similar degree of enhancement of metolachlor metabolism was observed in both a metolachlor-tolerant (’Cargill 7567’) and a metolachlor-susceptible (’Northrup-King 9283’) corn line. The total GSH content of shoots of the metolachlor-susceptible corn hybrid was not affected by benoxacor treatment, but an increase was noted for shoots of the tolerant corn hybrid. The two corn hybrids with differential tolerance to metolachlor also differ in their dose response to benoxacor with higher safener concentra­tions failing to induce or inhibit GST activity of the tolerant ’Cargill 7567’ corn line. Stimula­tion of GST activity and a corresponding enhanced rate of metolachlor metabolism can ac­count for the safening effect of benoxacor. These mechanism of action of dichloroacetamide safeners.

scholarly journals Endopeptidase 24.15 from rat testes. Isolation of the enzyme and its specificity toward synthetic and natural peptides, including enkephalin-containing peptides

1989 ◽  
Vol 261 (3) ◽  
pp. 951-958 ◽  
Author(s):  
M Orlowski ◽  
S Reznik ◽  
J Ayala ◽  
A R Pierotti
Keyword(s):  
Catalytic Efficiency ◽  
Enzymic Activity ◽  
Biologically Active ◽  
Active Peptides ◽  
Enzyme Substrate ◽  
Low Concentrations ◽  
Hydrophobic Amino Acids ◽  
Natural Peptides ◽  
Endopeptidase 24.15

Endopeptidase 24.15, a metalloendopeptidase (EC 3.4.24.15) with an Mr of about 70,000, was purified to homogeneity from rat testes. The enzyme cleaves preferentially bonds on the carboxyl side of hydrophobic amino acids. Secondary enzyme-substrate interactions at sites removed from the scissile bond are indicated by the finding that a hydrophobic or bulky residue in the P3′ position greatly contributes to substrate binding and catalytic efficiency. The isolated enzyme is inhibited by metal chelators and by thiols. Loss of enzymic activity after dialysis against EDTA can be restored by low concentrations of Zn2+ and Co2+ ions. The rate of reaction of the Co2+ enzyme with a synthetic substrate was higher than that of the Zn2+ enzyme. These results are consistent with the classification of the enzyme as a metalloendopeptidase. N-Carboxymethyl peptides that fulfil the binding requirements of the substrate recognition site of the enzyme act as potent competitive inhibitors. Biologically active peptides such as luteinizing hormone-releasing hormone, bradykinin and neurotensin are cleaved at sites consistent with the specificity of the enzyme deduced from studies with synthetic peptides. Dynorphin A (1-8)-peptide, beta-neoendorphin, metorphamide, and Metenkephalin-Arg6-Gly7-Leu8 are rapidly converted to the corresponding enkephalins. The testis enzyme is catalytically and immunologically closely related to the previously identified brain enzyme.

scholarly journals Peptides: Prospects for Use in the Treatment of COVID-19

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4389 ◽  
Author(s):  
Vladimir Khavinson ◽  
Natalia Linkova ◽  
Anastasiia Dyatlova ◽  
Boris Kuznik ◽  
Roman Umnov
Keyword(s):  
Side Effects ◽  
Chronic Diseases ◽  
Mechanism Of Action ◽  
Physiological Mechanism ◽  
Antimalarial Drugs ◽  
Multiple Organ ◽  
Severe Form ◽  
Pathological Process ◽  
Low Concentrations ◽  
Inflammatory Effect

There is a vast practice of using antimalarial drugs, RAS inhibitors, serine protease inhibitors, inhibitors of the RNA-dependent RNA polymerase of the virus and immunosuppressants for the treatment of the severe form of COVID-19, which often occurs in patients with chronic diseases and older persons. Currently, the clinical efficacy of these drugs for COVID-19 has not been proven yet. Side effects of antimalarial drugs can worsen the condition of patients and increase the likelihood of death. Peptides, given their physiological mechanism of action, have virtually no side effects. Many of them are geroprotectors and can be used in patients with chronic diseases. Peptides may be able to prevent the development of the pathological process during COVID-19 by inhibiting SARS-CoV-2 virus proteins, thereby having immuno- and bronchoprotective effects on lung cells, and normalizing the state of the hemostasis system. Immunomodulators (RKDVY, EW, KE, AEDG), possessing a physiological mechanism of action at low concentrations, appear to be the most promising group among the peptides. They normalize the cytokines’ synthesis and have an anti-inflammatory effect, thereby preventing the development of disseminated intravascular coagulation, acute respiratory distress syndrome and multiple organ failure.

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