scholarly journals Substrate specificity and modifications of the active centre of elastase-like neutral proteinases from horse blood leucocytes

1976 ◽  
Vol 153 (2) ◽  
pp. 397-402 ◽  
Author(s):  
A Koj ◽  
J Chudzik ◽  
A Dubin
Keyword(s):  
Methyl Ester ◽  
Substrate Specificity ◽  
Rose Bengal ◽  
Ph Dependence ◽  
Maximum Activity ◽  
Enzyme Molecule ◽  
Active Centre ◽  
Pancreatic Elastase ◽  
Horse Blood ◽  
Nitrophenyl Ester

Two proteinases (2A and 2B) purified from the granular fraction of horse blood leucocytes degrade casein (Km values 12.8 and 6mg/ml respectively) with maximum activity at pH 7.4 and in the presence of 2m-urea. Urea-denatured haemoglobin, fibrinogen, albumin and resorcin/fuchsin-stained elastin are digested at a slower rate. The enzymes hydrolyse synthetic substrates of elastase, N-benzyloxycarbonyl-L-alanine 4-nitrophenyl ester (Km 0.114 and 0.178 mM) and N-acetyl-tri-L-alanine methyl ester (Km 5.55 and 0.98 mM), but they do not hydrolyse synthetic substrates of trypsin, chymotrypsin and thrombin. The examined proteinases are completely inhibited by 2 mM-di-isopropyl phosphorfluoridate and show a sensitivity to butyl and octyl isocyanates similar to that of pancreatic elastase. The pH-dependence of their photoinactivation in the presence of Rose Bengal indicates the presence of histidine in the active centre. Proteinase 2A rather insensitive to iodination by IC1 as is pancreatic elastase, whereas proteinase 2B is totally inactivated after incorporation of five iodine atoms per enzyme molecule.

scholarly journals Cathepsin B, the lysosomal thiol proteinase of calf liver

1969 ◽  
Vol 114 (4) ◽  
pp. 673-678 ◽  
Author(s):  
O. Snellman
Keyword(s):  
Cathepsin B ◽  
Ph Dependence ◽  
Gel Filtration ◽  
Chelating Agent ◽  
Thiol Group ◽  
Maximum Activity ◽  
Active Centre ◽  
Peptide Bonds ◽  
Hydrolysis Of ◽  
Thiol Proteinase

Cathepsin B from calf liver was obtained by a method involving preparation of a lysosomal–mitochondrial pellet and treatment of this pellet with acetone. The material was extracted with an acid buffer, pH4·0, and then precipitated from the extract with acetone. The precipitate was dissolved in phosphate buffer, pH7·4, and subjected to gel filtration on Sephadex G-200 and G-100. The cathepsin B emerged in a range of molecular weight much lower than 50000 as a well-defined component. The purity of this material was checked by electrophoresis. To obtain maximum activity the enzyme had to be activated with a chelating agent and a reducing agent (i.e. EDTA and cysteine). A number of different substrates were used. The enzyme was active for the hydrolysis of both peptide bonds and ester bonds and had approximately equal reactivity in the two cases. The pH-dependence of the hydrolysis was the same with both substrates. The binding of the substrates was half-maximal at pH4·5 and at pH6·8. A thiol group occurred in the active centre but this group ought to have a much higher pK than that found in this enzyme.

scholarly journals Contribution of the active-site metal cation to the catalytic activity and to the conformational stability of phosphotriesterase: temperature- and pH-dependence

2004 ◽  
Vol 380 (3) ◽  
pp. 627-633 ◽  
Author(s):  
Daniel ROCHU ◽  
Nathalie VIGUIÉ ◽  
Frédérique RENAULT ◽  
David CROUZIER ◽  
Marie-Thérèse FROMENT ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Metal Cation ◽  
Active Site ◽  
Ph Dependence ◽  
Conformational Stability ◽  
Maximum Activity ◽  
Active Centre ◽  
Optimum Activity ◽  
Maximum Stability ◽  
Activation Phase

Phosphotriesterase (PTE) detoxifies nerve agents and organophosphate pesticides. The two zinc cations of the PTE active centre can be substituted by other transition metal cations without loss of activity. Furthermore, metal-substituted PTEs display differences in catalytic properties. A prerequisite for engineering highly efficient mutants of PTE is to improve their thermostability. Isoelectric focusing, capillary electrophoresis and steady-state kinetics analysis were used to determine the contribution of the active-site cations Zn2+, Co2+ or Cd2+ to both the catalytic activity and the conformational stability of the corresponding PTE isoforms. The three isoforms have different pI values (7.2, 7.5 and 7.1) and showed non-superimposable electrophoretic titration curves. The overall structural alterations, causing changes in functional properties, were found to be related to the nature of the bound cation: ionic radius and ion electronegativity correlate with Km and kcat respectively. In addition, the pH-dependent activity profiles of isoforms were different. The temperature-dependent profiles of activity showed maximum activity at T≤35 °C, followed by an activation phase near 45–48 °C and then inactivation which was completed at 60 °C. Analysis of thermal denaturation of the PTEs provided evidence that the activation phase resulted from a transient intermediate. Finally, at the optimum activity between pH 8 and 9.4, the thermostability of the different PTEs increased as the pH decreased, and the metal cation modulated stability (Zn2+-, Co2+- and Cd2+-PTE showed different Tm values of 60.5–67 °C, 58–64 °C and 53–64 °C respectively). Requirements for optimum activity of PTE (displayed by Co2+-PTE) and maximum stability (displayed by Zn2+-PTE) were demonstrated.

scholarly journals A new dopachrome-rearranging enzyme from the ejected ink of the cuttlefish Sepia officinalis.

1994 ◽  
Vol 299 (3) ◽  
pp. 839-844 ◽  
Author(s):  
A Palumbo ◽  
M d'Ischia ◽  
G Misuraca ◽  
L De Martino ◽  
G Prota
Keyword(s):  
Catalytic Activity ◽  
Methyl Ester ◽  
Substrate Specificity ◽  
Molecular Mass ◽  
Significant Inhibition ◽  
Single Band ◽  
Pigment Cells ◽  
Sepia Officinalis ◽  
High Substrate ◽  
Sds Page

A melanogenic enzyme catalysing the rearrangement of dopachrome has been identified in the ejected ink of the cuttlefish Sepia officinalis. This enzyme occurs as a heat-labile protein which co-migrates with tyrosinase under a variety of chromatographic and electrophoretic conditions. On SDS/PAGE it shows like a single band with an approx. molecular mass of 85 kDa. The enzyme possesses high substrate specificity, acting on L-dopachrome (Km = 1 mM at pH 6.8) and on L-alpha-methyl-dopachrome, but not on D-dopachrome, L-dopachrome methyl ester, dopaminochrome and adrenochrome. Significant inhibition of the catalytic activity was observed with tropolone and L-mimosine. H.p.1.c. analysis of the enzyme-catalysed rearrangement of L-dopachrome revealed the quantitative formation of the decarboxylated product, 5,6-dihydroxyindole. These results point to marked differences between melanogenesis in cephalopod pigment cells and in melanocytes, which may have important implications in relation to the use of sepiomelanin as a model for studies of mammalian melanins.

ÉTUDE DES EFFETS ÉLECTROSTATIQUES SUR LE MÉCANISME D'ACTION CATALYTIQUE DE LA PHOSPHATASE ALCALINE INTESTINALE DE VEAU

1965 ◽  
Vol 43 (8) ◽  
pp. 2222-2235 ◽  
Author(s):  
Michel Lazdunski ◽  
Jacques Brouillard ◽  
Ludovic Ouellet
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Maximum Activity ◽  
Enzyme Molecule ◽  
High Substrate Concentration ◽  
Nitrophenyl Phosphate ◽  
Phosphatase Alcaline ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Activated Complex

The influence of dioxane and ethanol on the rate of hydrolysis of p-nitrophenyl phosphate in the presence of an intestinal alcaline phosphatase can be interpreted as a dielectric constant effect, at high substrate concentration. The dielectric constant effect is a function of the pH of the medium and is maximum around pH 9.4 at 25 °C and pH 9.0 at 15 °C. An interpretation suggesting that the change in diameter of the enzyme molecule becoming an activated complex is minimum at a pH of maximum activity is proposed. The same model can take into account the influence of the ionic strength on the same reaction.

scholarly journals UDP-sugar Pyrophosphorylase with Broad Substrate Specificity Toward Various Monosaccharide 1-Phosphates from Pea Sprouts

2004 ◽  
Vol 279 (44) ◽  
pp. 45728-45736 ◽  
Author(s):  
Toshihisa Kotake ◽  
Daisuke Yamaguchi ◽  
Hiroshi Ohzono ◽  
Sachiko Hojo ◽  
Satoshi Kaneko ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Substrate Specificity ◽  
Molecular Mass ◽  
Glucuronic Acid ◽  
De Novo ◽  
Higher Plants ◽  
Maximum Activity ◽  
Broad Substrate Specificity ◽  
Salvage Pathways

UDP-sugars, activated forms of monosaccharides, are synthesized throughde novoand salvage pathways and serve as substrates for the synthesis of polysaccharides, glycolipids, and glycoproteins in higher plants. A UDP-sugar pyrophosphorylase, designated PsUSP, was purified about 1,200-fold from pea (Pisum sativumL.) sprouts by conventional chromatography. The apparent molecular mass of the purified PsUSP was 67,000 Da. The enzyme catalyzed the formation of UDP-Glc, UDP-Gal, UDP-glucuronic acid, UDP-l-arabinose, and UDP-xylose from respective monosaccharide 1-phosphates in the presence of UTP as a co-substrate, indicating that the enzyme has broad substrate specificity toward monosaccharide 1-phosphates. Maximum activity of the enzyme occurred at pH 6.5–7.5, and at 45 °C in the presence of 2 mmMg2+. The apparentKmvalues for Glc 1-phosphate andl-arabinose 1-phosphate were 0.34 and 0.96 mm, respectively.PsUSPcDNA was cloned by reverse transcriptase-PCR.PsUSPappears to encode a protein with a molecular mass of 66,040 Da (600 amino acids) and possesses a uridine-binding site, which has also been found in a human UDP-N-acetylhexosamine pyrophosphorylase. Phylogenetic analysis revealed that PsUSP can be categorized in a group together with homologues fromArabidopsisand rice, which is distinct from the UDP-Glc and UDP-N-acetylhexosamine pyrophosphorylase groups. Recombinant PsUSP expressed inEscherichia colicatalyzed the formation of UDP-sugars from monosaccharide 1-phosphates and UTP with efficiency similar to that of the native enzyme. These results indicate that the enzyme is a novel type of UDP-sugar pyrophosphorylase, which catalyzes the formation of various UDP-sugars at the end of salvage pathways in higher plants.

Fluorination of sulfur-containing amino acids: Reaction of xenon difluoride with cysteine derivatives

1990 ◽  
Vol 68 (3) ◽  
pp. 477-479 ◽  
Author(s):  
Xiaoling Huang ◽  
Barry J. Blackburn ◽  
Steve C. F. Au-Yeung ◽  
Alexander F. Janzen
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Methyl Ester ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Xenon Difluoride ◽  
Nitrophenyl Ester ◽  
Sulfur Containing

The reaction of XeF2 with cysteine derivatives RSCH2CH(NHR)COOR, i.e., S-benzyl-N-trifluoroacetyl-L-cysteine methyl ester, S-benzyl-N-carbobenzoxy-L-cysteine p-nitrophenyl ester, and S-methyl-N-trifluoroacetyl-L-cysteine methyl ester is described. The fluorinated products PhCHFSCH2CH(NHR)COOR, PhCH2SCHFCH(NHR)COOR, and FCH2SCH2CH(NHR)COOR were identified by 1H and 19F nuclear magnetic resonance spectroscopy. PhCH2SCHFCH(NHR)COOR loses HF within 24 hours to give Z- and E-PhCH2SCH=C(NHR)COOR. If the reaction with XeF2 is carried out in the presence of moisture the sulfoxide RS(O)CH2CH(NHR)COOR and sulfone RSO2CH2CH(NHR)COOR are produced. Keywords: fluorination, XeF2, amino acids, cysteine.

scholarly journals Substrate-specificity studies on protochlorophyllide reductase in barley (Hordeum vulgare) etioplast membranes

1980 ◽  
Vol 186 (1) ◽  
pp. 267-278 ◽  
Author(s):  
W T Griffiths
Keyword(s):  
Carboxylic Acid ◽  
Methyl Ester ◽  
Hordeum Vulgare ◽  
Substrate Specificity ◽  
Acid Group ◽  
Carboxylic Acid Group ◽  
Naturally Occurring ◽  
Protochlorophyllide Reductase ◽  
Nickel Copper ◽  
Etioplast Membranes

1. The substrate specificity of the enzyme protochlorophyllide reductase in barley (Hordeum vulgare) etioplasts was investigated. 2. It was shown that naturally occurring esterified protochlorophyllide and chemically prepared protochlorophyllide methyl ester are not substrates for the enzyme, suggesting an important role for the C-7 carboxylic acid group in binding of the porphyrin to the enzyme. 3. Removal of magnesium from the protochlorophyllide leads to inactivity of the compound as a substrate for the enzyme. However, activity can be restored by replacing the magnesium with zinc, whereas nickel, copper or cobalt failed to restore substrate activity. 4. Binding of the second substrate, NADPH, to the enzyme probably occurs through the 2'-phosphate group in the coenzyme.

scholarly journals Mechanistic Studies of the Yeast Polyamine Oxidase Fms1: Kinetic Mechanism, Substrate Specificity, and pH Dependence

Biochemistry ◽  
2010 ◽  
Vol 49 (49) ◽  
pp. 10440-10448 ◽  
Author(s):  
Mariya S. Adachi ◽  
Jason M. Torres ◽  
Paul F. Fitzpatrick
Keyword(s):  
Substrate Specificity ◽  
Ph Dependence ◽  
Kinetic Mechanism ◽  
Polyamine Oxidase ◽  
Mechanistic Studies
Sign in / Sign up

Export Citation Format

Share Document