scholarly journals THE ACTION OF ALPHA CHYMOTRYPSIN UPON MIXTURES OF ESTERS AND PROTEINS AT ENZYME-SATURATING CONCENTRATIONS

1958 ◽  
Vol 42 (1) ◽  
pp. 49-68 ◽  
Author(s):  
M. Castañeda-Agulló ◽  
Luz M. del Castillo
Keyword(s):  
Active Center ◽  
Active Sites ◽  
Saturation Level ◽  
Simultaneous Presence ◽  
Protein Substrates ◽  
Mechanism Of Inhibition ◽  
Hydrolysis Of ◽  
Chemical Evidence

The behavior of α-chymotrypsin has been studied in the simultaneous presence of two different substrates, each present in the reaction mixture at its saturation level. Mixtures of two esters were hydrolyzed at rates intermediate between the rates of hydrolysis of each ester when present alone, suggesting, in this case, competitive hydrolysis. In contrast, the rates of hydrolysis in mixtures of casein with gelatin or of either protein with an ester were equal to the sum of the rates of hydrolysis of the separate substrates, indicating in these cases independent hydrolysis. The activity of the α-chymotrypsin preparation used could not be attributed to contamination with other enzymes. Studies of the effect of soy bean inhibitor on chymotrypsin indicate that the mechanism of inhibition with protein substrates differs from that when esters are used, providing further evidence that α-chymotrypsin reacts differently with esters and proteins. These results indicate that if chymotrypsin forms specific complexes with its substrates, it must possess at least three distinct active sites. However there is independent chemical evidence that the proteolytic and esterolytic activities of this enzyme reside in the same active center. If this is true, the experimental observations reported here cannot be explained unless it is supposed that this enzyme does not form specific Michaelis complexes with its substrates.

Kinetic Study of the Effect of Heparin on the Amidase Activity of Trypsin, Plasmin and Urokinase

1983 ◽  
Vol 49 (03) ◽  
pp. 199-203 ◽  
Author(s):  
V M Yomtova ◽  
N A Stambolieva ◽  
B M Blagoev
Keyword(s):  
Kinetic Study ◽  
Active Center ◽  
Simultaneous Presence ◽  
Amidase Activity ◽  
Competitive Inhibitors ◽  
Uncompetitive Inhibitor

SummaryIt was found that the effect of heparin on the amidase activity of urokinase (E C 3.4.21.31), plasmin (E C 3.4.21.7) and trypsin (E C 3.4.21.4) depended on the substrate used. No effect of heparin on the amidase activity of urokinase and trypsin was observed when Pyro Glu-Gly-Arg-p-nitroanilide (S-2444) and α-N-acetyl-L-lysine-p-nitroanilide (ALNA) were used as substrates. Heparin acted as a uncompetitive inhibitor of trypsin (Ki = 1.2×10-6 M), plasmin (Ki = 4.9×10-6 M) and urokinase (Ki = l.0×10-7 M) when Bz-Phe-Val-Arg-p-nitroanilide (S-2160), H-D-Val-Leu-Lys-p-nitroanilide (S-2251) and plasminogen, respectively, were used as substrates. These results, as well as the data obtained by studying the effect of the simultaneous presence of heparin and competitive inhibitors suggest that although heparin is not bound at the active center of these enzymes, it may influence the effectivity of catalysis.

Effect of Modifiers on the Hydrolysis of Basic and Neutral Peptides by Carboxypeptidase B

1975 ◽  
Vol 53 (7) ◽  
pp. 747-757 ◽  
Author(s):  
Graham J. Moore ◽  
N. Leo Benoiton
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Kinetic Behavior ◽  
Carboxypeptidase A ◽  
Phenyllactic Acid ◽  
Carboxypeptidase B ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Basic Peptides ◽  
Hydrolysis Of

The initial rates of hydrolysis of Bz-Gly-Lys and Bz-Gly-Phe by carboxypeptidase B (CPB) are increased in the presence of the modifiers β-phenylpropionic acid, cyclohexanol, Bz-Gly, and Bz-Gly-Gly. The hydrolysis of the tripeptide Bz-Gly-Gly-Phe is also activated by Bz-Gly and Bz-Gly-Gly, but none of these modifiers activate the hydrolysis of Bz-Gly-Gly-Lys, Z-Leu-Ala-Phe, or Bz-Gly-phenyllactic acid by CPB. All modifiers except cyclohexanol display inhibitory modes of binding when present in high concentration.Examination of Lineweaver–Burk plots in the presence of fixed concentrations of Bz-Gly has shown that activation of the hydrolysis of neutral and basic peptides by CPB, as reflected in the values of the extrapolated parameters, Km(app) and keat, occurs by different mechanisms. For Bz-Gly-Gly-Phe, activation occurs because the enzyme–modifier complex has a higher affinity than the free enzyme for the substrate, whereas activation of the hydrolysis of Bz-Gly-Lys derives from an increase in the rate of breakdown of the enzyme–substrate complex to give products.Cyclohexanol differs from Bz-Gly and Bz-Gly-Gly in that it displays no inhibitory mode of binding with any of the substrates examined, activates only the hydrolysis of dipeptides by CPB, and has a greater effect on the hydrolysis of the basic dipeptide than on the neutral dipeptide. Moreover, when Bz-Gly-Lys is the substrate, cyclohexanol activates its hydrolysis by CPB by increasing both the enzyme–substrate binding affinity and the rate of the catalytic step, an effect different from that observed when Bz-Gly is the modifier.The anomalous kinetic behavior of CPB is remarkably similar to that of carboxypeptidase A, and is a good indication that both enzymes have very similar structures in and around their respective active sites. A binding site for activator molecules down the cleft of the active site is proposed for CPB to explain the observed kinetic behavior.

scholarly journals Influence of Me2SO and incubation time on papain activity studied using fluorogenic substrates.

2001 ◽  
Vol 48 (4) ◽  
pp. 995-1002 ◽  
Author(s):  
M Szabelski ◽  
K Stachowiak ◽  
W Wiczk
Keyword(s):  
Incubation Time ◽  
Active Sites ◽  
Initial Rate ◽  
Substrate Binding ◽  
Rapid Decrease ◽  
Fluorogenic Substrates ◽  
Binding Process ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Papain activity in a buffer containing Me2SO was studied using fluorogenic substrates. It was found that the number of active sites of papain decreases with increasing Me2SO concentration whereas the incubation time, in a buffer containing 3% Me2SO does not affect the number of active sites. However, an increase of papain incubation time in the buffer with 3% Me2SO decreased the initial rate of hydrolysis of Z-Phe-Arg-Amc as well as Dabcyl-Lys-Phe-Gly-Gly-Ala-Ala-Edans. Moreover, an increase of Me2SO concentration in working buffer decreased the initial rate of papain-catalysed hydrolysis of both substrates. A rapid decrease of the initial rate (by up to 30%) was observed between 1 and 2% Me2SO. Application of the Michaelis-Menten equation revealed that at the higher Me2SO concentrations the apparent values of k(cat)/Km decreased as a result of Km increase and kcat decrease. However, Me2SO changed the substrate binding process more effectively (Km) than the rate of catalysis k(cat).

New insights into lactase and glycosylceramidase activities of rat lactase-phlorizin hydrolase

1989 ◽  
Vol 257 (4) ◽  
pp. G616-G623 ◽  
Author(s):  
H. A. Buller ◽  
A. G. Van Wassenaer ◽  
S. Raghavan ◽  
R. K. Montgomery ◽  
M. A. Sybicki ◽  
...  
Keyword(s):  
Active Sites ◽  
Specific Activity ◽  
Fold Increase ◽  
Developmental Pattern ◽  
Lactose Hydrolysis ◽  
Adult Males ◽  
Lactase Activity ◽  
Developmental Patterns ◽  
Catalytic Sites ◽  
Hydrolysis Of

Lactase-phlorizin hydrolase, a small intestinal disaccharidase, has been considered mainly an enzyme important only for the hydrolysis of lactose. After weaning in most mammals lactase-specific activity falls markedly, and, functionally, adult mammals are considered to be lactase deficient. However, the persistence of low levels of lactase activity in adulthood has never been explained. In addition, it has been suggested that lactase-phlorizin hydrolase is associated with glycosylceramidase activity when the enzyme is prepared by column chromatography, but it is unclear whether this represents copurified activities or two catalytic sites on one peptide. The developmental patterns of lactase-phlorizin hydrolase and other disaccharidases were investigated in homogenates of total rat small intestine; lactase and several glycosylceramidases were measured in immunoprecipitates from these homogenates using a monoclonal antibody. The developmental pattern of total lactase activity showed a steady 2.3-fold increase to adult levels (specific activity decreased eightfold), whereas total phlorizin-hydrolase activity increased 10.7-fold (specific activity decreased threefold). As expected, levels of both total and specific sucrase and maltase activities increased during development. In lactating rats total lactase activity showed a significant increase compared with adult males. The developmental pattern of the enzyme activities for the glycolipid substrates was similar to that found for lactase, and the immunoprecipitated enzyme showed a 40- to 55-fold higher affinity for the glycolipids than for lactose. Galactosyl- and lactosylceramide inhibited lactose hydrolysis by 38%, without a competitive pattern, suggesting two different active sites for lactose and glycolipid hydrolysis, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycosides from Cephalaria Species

2010 ◽  
Vol 65 (11) ◽  
pp. 1384-1392 ◽  
Author(s):  
Erkan Halay ◽  
Süheyla Kırmızıgül
Keyword(s):  
Mass Spectrometry ◽  
Oleanolic Acid ◽  
2D Nmr ◽  
Spectroscopic Methods ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Nmr Techniques ◽  
Basic Hydrolysis ◽  
Hydrolysis Of ◽  
Chemical Evidence

Three novel triterpene glycosides (1 - 3), namely lycicoside I, II and cilicicoside I, were isolated from two different Cephalaria (Dipsacaceae) species along with one known oleanane- and one iridoit- type of glycoside. The structures of these compounds were established as 3-O-[β -D-glucopyranosyl( 1→3)-α-L-rhamnopyranosyl(1→4)-β -D-xylopyranosyl(1→4)-β -D-xylopyranosyl]-28-O-[β -Dglucopyranosyl( 1→6)-β -D-glucopyranosyl]-oleanolic acid (1), 3-O-[β -D-xylopyranosyl(1→3)-α- L-rhamnopyranosyl(1→4)-β -D-xylopyranosyl]-28-O-[β -D-glucopyranosyl]-oleanolic acid (2) from Cephalaria lycica Matthew and 3-O-{β -D-glucopyranosyl(1→4)-β -D-xylopyranosyl(1→3)-α-Lrhamnopyranosyl( 1→2)-[β -D-glucopyranosyl(1→3)]-α -L-rhamnopyranosyl}-28-O-[β -D-glucopyranosyl( 1→6)-β -D-glucopyranosyl]-hederagenin (3) from Cephalaria cilicica Boiss. & Kotschy, on the basis of spectroscopic methods (1D and 2D NMR techniques, mass spectrometry) and chemical evidence. In addition, three new prosapogenins, 1B - 3B, were obtained from the basic hydrolysis of 1 - 3. The antimicrobial activity of 1 - 3 was tested against some Gram-positive and Gram-negative bacteria strains.

Further Investigations on the p-Nitrophenylphosphatase Activity of Intact Ehrlich Ascites Tumor Cells

1978 ◽  
Vol 33 (3-4) ◽  
pp. 227-230 ◽  
Author(s):  
Reiner Merz ◽  
Monika Löffler ◽  
Friedhelm Schneider
Keyword(s):  
Tumor Cells ◽  
Active Sites ◽  
Ehrlich Ascites Tumor ◽  
Ehrlich Ascites Tumor Cells ◽  
Ascites Tumor ◽  
Intact Cells ◽  
Blocking Agents ◽  
Ehrlich Ascites ◽  
Eat Cells ◽  
Hydrolysis Of

The substrate specificity and the effects of nucleotides and SH-blocking agents on the p-nitro- phenylphosphatase activity of intact Ehrlich ascites tumor cells (EAT) cells were studied, ᴅʟ-β- Glycerophosphate, o-phosphoethanolamine, cholinephosphate, glucose-6-phosphate, o-carboxyphenyl- phosphate,, phosphoenolpyruvate and AMP were not attacked by intact cells. ATP > GTP > UTP > PPi > pNPP were cleaved with decreasing velocity. A stimulation of the cleavage of p-NPP by the following nucleotides was observed with decreasing effectivity: ATP > ADP > GTP > UTP; AMP was ineffective. The phosphatase activity was not affected by malate, tartrate and glutathion disulfide. The SH blocking agents diamide and thimerosal were more effective in­hibitors of the pNPPase than of the ATPase activity, whereas the hydrolysis of ATP is more affected by the ATP analog adenylylimidodiphosphate. The present data are best compatible with a double headed enzyme: Both active sites interact with ATP, only one is active against p-NPP and sensitive against SH-blocking agents.

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