scholarly journals THE ACTION OF ENZYMES ON RHODOPSIN

1958 ◽  
Vol 42 (2) ◽  
pp. 371-383 ◽  
Author(s):  
Charles M. Radding ◽  
George Wald
Keyword(s):  
Pancreatic Lipase ◽  
Cage Effect ◽  
Enzyme Molecule ◽  
Amino Groups ◽  
Peptide Bonds ◽  
Rhodopsin Molecule ◽  
Solvent Molecules ◽  
Rapid Hydrolysis ◽  
Two Stages ◽  
Hydrolysis Of

The effects have been examined of chymotrypsin, pepsin, trypsin, and pancreatic lipase on cattle rhodopsin in digitonin solution. The digestion of rhodopsin by chymotrypsin was measured by the hydrolysis of peptide bonds (formol titration), changes in pH, and bleaching. The digestion proceeds in two stages: an initial rapid hydrolysis which exposes about 30 amino groups per molecule, without bleaching; superimposed on a slower hydrolysis which exposes about 50 additional amino groups, with proportionate bleaching. The chymotryptic action begins at pH about 6.0 and increases logarithmically in rate to pH 9.2. Trypsin and pepsin also bleach rhodopsin in solution. A preparation of pancreatic lipase bleached it slightly, but no more than could be explained by contamination with proteases. In digitonin solution each rhodopsin molecule is associated in a micelle with about 200 molecules of digitonin; yet the latter do not appear to hinder enzyme action. It is suggested that the digitonin sheath is sufficiently fluid to be penetrated on collision with an enzyme molecule; and that once together the enzyme and substrate are held together by intermolecular attractive forces, and by the "cage effect" of bombardment by surrounding solvent molecules. The two stages of chymotryptic digestion of rhodopsin may correspond to an initial rapid fragmentation, such as has been observed with many proteinases and substrates; superimposed upon a slower digestion of the fragments. Since the first phase involves no bleaching, this may mean that rhodopsin can be broken into considerably smaller fragments without loss of optical properties.

THE PROTEOLYTIC ENZYMES OF MICROORGANISMS: III. SOME CHARACTERISTICS OF EXTRACELLULAR PROTEASES PRODUCED IN SUBMERGED CULTURE

1950 ◽  
Vol 28c (6) ◽  
pp. 600-612 ◽  
Author(s):  
W. B. McConnell
Keyword(s):  
Low Temperatures ◽  
Free Amino ◽  
Submerged Culture ◽  
Culture Medium ◽  
Proteolytic Enzymes ◽  
Amino Groups ◽  
Extracellular Proteases ◽  
Egg Albumin ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

Some of the general characteristics of the proteases liberated into the culture medium by molds and actinomycetes grown in submerged culture have been studied. Species of Alternaria, Streptomyces, Mortierella, and Gliocladium were used. The enzymes resemble trypsin in that they are most active at a pH slightly above 7 and are inhibited by a preparation of egg albumin. They are stable at low temperatures but suffer marked losses in activity when stored for 16 hr. above 40 °C. The most rapid hydrolysis of gelatin occurs at temperatures between 40 °C. and 50 °C. The enzymes from different organisms show definite differences with respect to their ability to attack different proteins, gelatin and casein being in general the most readily digested. The protease systems from different organisms also vary with respect to the extent to which they can digest gelatin; some enzymes are able to release about three times as many amino groups from gelatin as others. The limit of the hydrolysis is not dependent upon substrate concentration but is slightly affected by the concentration of enzyme. The enzymes were effective in liberating free amino acids from gelatin.

Effect of protein content on low temperature inactivation of the extracellular proteinase from Pseudomonas fluorescens 22F

1998 ◽  
Vol 65 (2) ◽  
pp. 347-352 ◽  
Author(s):  
ERIX P. SCHOKKER ◽  
MARTINUS A. J. S. VAN BOEKEL
Keyword(s):  
Pseudomonas Fluorescens ◽  
Limited Proteolysis ◽  
Sodium Caseinate ◽  
Competitive Inhibitor ◽  
Amino Acid Residues ◽  
Enzyme Molecule ◽  
Extracellular Proteinase ◽  
Peptide Bonds ◽  
Enzyme Solution ◽  
Hydrolysis Of

Previously we have examined the inactivation of unpurified extracellular proteinase from Pseudomonas fluorescens 22F diluted in demineralized water (Schokker & van Boekel, 1998) in the range 40–70°C. It appeared that the inactivation was most probably caused by intermolecular autoproteolysis, which is the hydrolysis of unfolded proteinase molecules by native (not yet unfolded) molecules. It has been reported that purification of proteinases from Pseudomonas spp. enhances the susceptibility of the proteinase to autoproteolysis (Barach et al. 1976; Griffiths et al. 1981; Leinmüller & Christophersen, 1982; Kroll, 1989; Kumura et al. 1991). On the other hand, when the proteinase is heated in milk or when proteins are added to the enzyme solution, the rate of inactivation by autoproteolysis diminishes (Barach et al. 1978; Kroll & Klostermeyer, 1984; Stepaniak et al. 1991). Apparently, proteins stabilize the proteinase against inactivation by autoproteolysis.Substrate or other ligands stabilize many enzymes against limited proteolysis. Binding of these substances to the enzyme molecule, either to the catalytic centre or to amino acid residues on the enzyme molecule surface, may impose steric difficulties so that the susceptible peptide bonds are protected against proteolysis (Mihalyi, 1978). Such binding may also cause a conformational change of the enzyme molecule, such that susceptible peptide bonds cannot be attacked or that the conformation is stabilized against unfolding (Mihalyi, 1978). In the latter case an increase in the denaturation temperature (Td) would be expected.In the case of proteinases, addition of substrate to the enzyme solution may protect the enzyme by a third mechanism. Besides autoproteolysis of the proteinase, the added proteins can be digested. An enzyme molecule digesting a protein is not available at the same time for autoproteolysis, so that the substrate may act as a competitive inhibitor against autoproteolysis.The aim of this study was to determine the mechanism of protection of the proteinase from Ps. fluorescens 22F by sodium caseinate.

scholarly journals TESTS FOR HYDROLYSIS OF PEPTIDE BONDS BY ULTRAVIOLET LIGHT

1950 ◽  
Vol 187 (2) ◽  
pp. 543-545
Author(s):  
Dorothy J. McLean ◽  
Arthur C. Giese
Keyword(s):  
Ultraviolet Light ◽  
Peptide Bonds ◽  
Hydrolysis Of

scholarly journals “Newton’s cradle” proton relay with amide–imidic acid tautomerization in inverting cellulase visualized by neutron crystallography

2015 ◽  
Vol 1 (7) ◽  
pp. e1500263 ◽  
Author(s):  
Akihiko Nakamura ◽  
Takuya Ishida ◽  
Katsuhiro Kusaka ◽  
Taro Yamada ◽  
Shinya Fushinobu ◽  
...  
Keyword(s):  
Glycoside Hydrolases ◽  
Side Chain ◽  
Enzymatic Reactions ◽  
X Ray Diffraction ◽  
Peptide Bonds ◽  
Proton Relay ◽  
Newton’S Cradle ◽  
Dynamics Simulations ◽  
Hydrolysis Of

Hydrolysis of carbohydrates is a major bioreaction in nature, catalyzed by glycoside hydrolases (GHs). We used neutron diffraction and high-resolution x-ray diffraction analyses to investigate the hydrogen bond network in inverting cellulase PcCel45A, which is an endoglucanase belonging to subfamily C of GH family 45, isolated from the basidiomycete Phanerochaete chrysosporium. Examination of the enzyme and enzyme-ligand structures indicates a key role of multiple tautomerizations of asparagine residues and peptide bonds, which are finally connected to the other catalytic residue via typical side-chain hydrogen bonds, in forming the “Newton’s cradle”–like proton relay pathway of the catalytic cycle. Amide–imidic acid tautomerization of asparagine has not been taken into account in recent molecular dynamics simulations of not only cellulases but also general enzyme catalysis, and it may be necessary to reconsider our interpretation of many enzymatic reactions.

Theoretical study on the role of cooperative solvent molecules in the neutral hydrolysis of ketene

2010 ◽  
Vol 127 (5-6) ◽  
pp. 493-506 ◽  
Author(s):  
Xiao-Peng Wu ◽  
Xi-Guang Wei ◽  
Xiao-Ming Sun ◽  
Yi Ren ◽  
Ning-Bew Wong ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Solvent Molecules ◽  
Hydrolysis Of
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