A crystallographic study of the oxidation of lysozyme by iodine

1967 ◽  
Vol 167 (1009) ◽  
pp. 435-438 ◽  
Keyword(s):  
Active Site ◽  
The Other ◽  
Enzymic Hydrolysis ◽  
Substrate Modification ◽  
Crystallographic Study ◽  
Competitive Inhibitors ◽  
Plausible Hypothesis ◽  
The One ◽  
Hydrolysis Of ◽  
Tryptophanyl Residue

The crystallographic examinations of the lysozyme molecule, and of the complexes of lysozyme with competitive inhibitors, have resulted in the identification of the active site and in a plausible hypothesis for its activity as described in the previous papers at this meeting (Blake, Mair, North, Phillips & Sarma, p. 365; Blake, Johnson, Mair, North, Phillips & Sarma, p. 378). The active site includes three tryptophanyl residues (62, 63 and 108) which appear to be involved in the binding of the substrate. Modification of some or all of these residues may provide further evidence of their function in the activity of the enzyme (see figure 19 a of Blake et al ., p. 384). Hartdegen & Rupley (1964) showed that the action of small amounts of triiodide produced two modified lysozymes. One product, containing iodine, was enzymically active, while the other which contained no iodine was inactive. Enzymic hydrolysis of the latter product revealed that it had one less tryptophanyl residue than the native enzyme. Hartdegen & Rupley were not able, however, to show which of the six tryptophanyl residues in the lysozyme molecule was the one uniquely reactive to iodine, but they were able to show that it was part of, or near, the active site.

scholarly journals Kinetic probes for inter-domain co-operation in human somatic angiotensin-converting enzyme

2005 ◽  
Vol 391 (3) ◽  
pp. 641-647 ◽  
Author(s):  
Olga E. Skirgello ◽  
Peter V. Binevski ◽  
Vladimir F. Pozdnev ◽  
Olga A. Kost
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Enzymatic Activity ◽  
Active Site ◽  
The Other ◽  
Converting Enzyme ◽  
Human Enzyme ◽  
Independent Functions ◽  
The Common ◽  
The Individual ◽  
Hydrolysis Of

s-ACE (the somatic form of angiotensin-converting enzyme) consists of two homologous domains (N- and C-domains), each bearing a catalytic site. Negative co-operativity between the two domains has been demonstrated for cow and pig ACEs. However, for the human enzyme there are conflicting reports in the literature: some suggest possible negative co-operativity between the domains, whereas others indicate independent functions of the domains within s-ACE. We demonstrate here that a 1:1 stoichiometry for the binding of the common ACE inhibitors, captopril and lisinopril, to human s-ACE is enough to abolish enzymatic activity towards FA {N-[3-(2-furyl)acryloyl]}-Phe-GlyGly, Cbz (benzyloxycarbonyl)-Phe-His-Leu or Hip (N-benzoylglycyl)-His-Leu. The kinetic parameters for the hydrolysis of seven tripeptide substrates by human s-ACE appeared to represent average values for parameters obtained for the individual N- and C-domains. Kinetic analysis of the simultaneous hydrolysis of two substrates, Hip-His-Leu (S1) and Cbz-Phe-His-Leu (S2), with a common product (His-Leu) by s-ACE at different values for the ratio of the initial concentrations of these substrates (i.e. σ=[S2]0/[S1]0) demonstrated competition of these substrates for binding to the s-ACE molecule, i.e. binding of a substrate at one active site makes the other site unavailable for either the same or a different substrate. Thus the two domains within human s-ACE exhibit strong negative co-operativity upon binding of common inhibitors and in the hydrolysis reactions of tripeptide substrates.

scholarly journals GMP and IMP Are Competitive Inhibitors of CMY-10, an Extended-Spectrum Class C β-Lactamase

2017 ◽  
Vol 61 (5) ◽  
Author(s):  
Jung-Hyun Na ◽  
Young Jun An ◽  
Sun-Shin Cha
Keyword(s):  
Crystal Structure ◽  
Active Site ◽  
Binding Mode ◽  
Competitive Inhibitor ◽  
Phosphate Group ◽  
The Other ◽  
Extended Spectrum ◽  
Competitive Inhibitors ◽  
Class C

ABSTRACT Nucleotides were effective in inhibiting the class C β-lactamase CMY-10. IMP was the most potent competitive inhibitor, with a Ki value of 16.2 μM. The crystal structure of CMY-10 complexed with GMP or IMP revealed that nucleotides fit into the R2 subsite of the active site with a unique vertical binding mode where the phosphate group at one terminus is deeply bound in the subsite and the base at the other terminus faces the solvent.

scholarly journals A comparison of the active site of maltase-glucoamylase from the brush border of rabbit small intestine and kidney by chemical modification studies

1991 ◽  
Vol 274 (2) ◽  
pp. 349-354 ◽  
Author(s):  
B Pereira ◽  
S Sivakami
Keyword(s):  
Chemical Modification ◽  
Brush Border ◽  
Active Site ◽  
Brush Border Membrane ◽  
Kidney Enzyme ◽  
Rabbit Intestine ◽  
Rabbit Small Intestine ◽  
Intestinal Enzyme ◽  
The One ◽  
Hydrolysis Of

The neutral maltase-glucoamylase complex has been purified to homogeneity from the brush-border membrane of rabbit intestine and kidney. Chemical modification of the amino acid side chains was carried out on the purified enzymes. Studies on the kidney enzyme revealed that tryptophan, histidine and cysteine were essential for both maltase and glucoamylase activities, whereas tryptophan, histidine and lysine were essential for the maltase and glucoamylase activities of the intestinal enzyme. Though there was no difference in the amino acids essential for the hydrolysis of maltose and starch by any one enzyme, starch hydrolysis seems to require two histidine residues instead of the one which is required for maltose hydrolysis. This appears to be true for both the intestinal and kidney enzymes.

Length of the active-site crossover loop defines the substrate specificity of ubiquitin C-terminal hydrolases for ubiquitin chains

2011 ◽  
Vol 441 (1) ◽  
pp. 143-149 ◽  
Author(s):  
Zi-Ren Zhou ◽  
Yu-Hang Zhang ◽  
Shuai Liu ◽  
Ai-Xin Song ◽  
Hong-Yu Hu
Keyword(s):  
Substrate Specificity ◽  
Active Site ◽  
Dependent Manner ◽  
Deubiquitinating Enzymes ◽  
Chain Flexibility ◽  
Isopeptide Bond ◽  
Short Loop ◽  
The One ◽  
Isopeptidase Activity ◽  
Hydrolysis Of

UCHs [Ub (ubiquitin) C-terminal hydrolases] are a family of deubiquitinating enzymes that are often thought to only remove small C-terminal peptide tails from Ub adducts. Among the four UCHs identified to date, neither UCH-L3 nor UCH-L1 can catalyse the hydrolysis of isopeptide Ub chains, but UCH-L5 can when it is present in the PA700 complex of the proteasome. In the present paper, we report that the UCH domain of UCH-L5, different from UCH-L1 and UCH-L3, by itself can process the K48-diUb (Lys48-linked di-ubiquitin) substrate by cleaving the isopeptide bond between two Ub units. The catalytic specificity of the four UCHs is dependent on the length of the active-site crossover loop. The UCH domain with a long crossover loop (usually >14 residues), such as that of UCH-L5 or BAP1 [BRCA1 (breast cancer early-onset 1)-associated protein 1], is able to cleave both small and large Ub derivatives, whereas the one with a short loop can only process small Ub derivatives. We also found that elongation of the crossover loop enables UCH-L1 to have isopeptidase activity for K48-diUb in a length-dependent manner. Thus the loop length of UCHs defines their substrate specificity for diUb chains, suggesting that the chain flexibility of the crossover loop plays an important role in determining its catalytic activity and substrate specificity for cleaving isopeptide Ub chains.

Characterization Of The Active Site Of Urokinase With A Series Of Potent Inhibitory Amidines

1981 ◽  
Author(s):  
J D Geratz ◽  
S R Shaver ◽  
R R Tidwell
Keyword(s):  
Active Site ◽  
Factor Xa ◽  
Selective Inhibition ◽  
The Other ◽  
Plasminogen Activation ◽  
Steric Factors ◽  
The Difference ◽  
The One ◽  
Striking Contrast

Twenty amidine-substituted indole-like heterocycles were synthesized and examined for their blocking effect against human urokinase and a number of related arginine- or lysine- directed proteases. Kinetic analyses were carried out with the help of peptide anilide substrates and revealed a reversible competitive inhibitory pattern with each compound. The Ki values were therefore interpreted to reflect binding conditions at the active site of the enzymes.A highly potent inhibitor of urokinase was discovered in 5-amidino-l-(4-amidinobenzyl)indole which proved to be 18 times more effective on a molar basis than p-aminobenzamidine and 150 times more effective than benzamidine. The Ki value at 37°C and pH 8.3 was determined as 3.2 × 10-6 M. In striking contrast to the findings with the other proteases studied, urokinase was very sensitive to inhibition by 6-amidinoindoline (Ki 1.8 × 10-5 M), yet was much less susceptible to inhibition by the fully unsaturated analog 6-amidinoindole. Steric factors resulting from the difference in planarity between the two compounds are held responsible for this observation. In plasminogen activation assays the antiurokinase effect of the heterocycles mirrored their potency in the assays employing the synthetic urokinase substrate.The significant differences in the inhibitory activities of amidines against urokinase, on the one hand, and plasmin, thrombin and factor Xa, on the other hand, will be useful for experiments where selective inhibition of plasminogen activation is to be achieved. The compounds will also be of help in characterizing other tissue activators with respect to urokinase.

scholarly journals Intramolecular distances between tryptophan residues and the active-site serine residue in alkaline bacterial proteinases as measured by fluorescence energy-transfer studies

1983 ◽  
Vol 215 (2) ◽  
pp. 413-416 ◽  
Author(s):  
N C Genov ◽  
M Shopova ◽  
R Boteva ◽  
F Ricchelli ◽  
G Jori
Keyword(s):  
Energy Transfer ◽  
Active Site ◽  
Three Dimensional ◽  
The Other ◽  
Fluorescence Energy Transfer ◽  
Serine Residue ◽  
Tryptophan Residues ◽  
The One ◽  
Fluorescence Energy

Singlet-singlet energy transfer from the tryptophan residues to an active-site-serine-bound 5-dimethylaminonaphthalene-1-sulphonyl group was investigated in four subtilisins. The transfer distances for subtilisin Novo and mesentericopeptidase are 1.93 +/- 0.20 nm (19.3 +/- 2.0 A) and 1.81 +/- 0.20 nm (18.1 +/- 2.0 A) respectively. The positions of the indole groups in the three-dimensional structures of the two pairs of proteinases, namely subtilisin Novo and mesentericopeptidase on the one hand and subtilisins Carlsberg and DY on the other, are essentially identical.

THE WHEAT LEAF PHOSPHATASES: VI. SOME PROPERTIES OF THE ENZYME SYSTEM HYDROLYZING ADENOSINE-5′-PHOSPHATE AND PHENOLPHTHALEIN DIPHOSPHATE IN CRUDE JUICE PREPARATIONS

1963 ◽  
Vol 41 (5) ◽  
pp. 1275-1281 ◽  
Author(s):  
D. W. A. Roberts
Keyword(s):  
Enzyme System ◽  
The Other ◽  
Enzymic Hydrolysis ◽  
Ph Optimum ◽  
Wheat Leaf ◽  
Hydrolysis Of ◽  
Leaf Juice

At least two enzymes are probably involved in the hydrolysis of mixtures of β-glycerophosphate, phenolphthalein diphosphate, and adenosine-5′-phosphate. One enzyme is primarily responsible for the hydrolysis of β-glycerophosphate whereas the other enzyme hydrolyzes adenosine-5′-phosphate and phenolphthalein diphosphate but has little activity on β-glycerophosphate.The liberation of orthophosphate from adenosine-5′-phosphate and phenolphthalein diphosphate by the enzyme in wheat leaf juice is inhibited by 0.005 M adenosine but not by 0.02 M phosphate. The inhibition of this enzyme by fluoride is markedly smaller than the inhibition of β-glycerophosphatase. The enzyme that hydrolyzes phenolphthalein diphosphate transfers phosphate from phenolphthalein diphosphate to adenosine to form adenosine-5′-phosphate.Experiments on the pH optimum for the enzymic hydrolysis of both adenosine-5′-phosphate and phenolphthalein diphosphate by undialyzed and dialyzed juice preparations with or without added Mg++ suggest that there may be more than one enzyme with different pH optima acting on both adenosine-5′-phosphate and phenolphthalein diphosphate.

Enzymic Hydrolysis of Methyl 2,3-O-Acetyl-5-Deoxy-α and β-D-Xylofuranosides - An Active-Site Model of Pig Liver Esterase

1997 ◽  
Vol 16 (7) ◽  
pp. 1011-1028 ◽  
Author(s):  
Jitka Moravcová ◽  
Zita Vanclová ◽  
Jindra Čapková ◽  
Karel Kefurt ◽  
Jan Staněk
Keyword(s):  
Active Site ◽  
Enzymic Hydrolysis ◽  
Pig Liver ◽  
Pig Liver Esterase ◽  
Site Model ◽  
Liver Esterase ◽  
Active Site Model ◽  
Hydrolysis Of
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