Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Primary amines react with 2,4-pentanedione at pH 6-9 to form enamines, N-alkyl-4-amino-3-penten-2-ones. The latter compounds readily regenerate the primary amine at low pH or on treatment with hydroxylamine. Guanidine and substituted guanidines react with 2,4-pentanedione to form N-substituted 2-amino-4,6-dimethylpyrimidines at a rate which is lower by at least a factor of 20 than the rate of reaction of 2,4-pentanedione with primary amines. Selective modification of lysine and arginine side chains in proteins can readily be achieved with 2,4-pentanedione. Modification of lysine is favored by reaction at pH 7 or for short reaction times at pH 9. Selective modification of arginine is achieved by reaction with 2,4-pentanedione for long times at pH 9, followed by treatment of the protein with hydroxylamine. The extent of modification of lysine and arginine side chains can readily be measured spectrophotometrically. Modification of lysozyme with 2,4-pentanedione at pH 7 results in modification of 3.8 lysine residues and less than 0.4 arginine residue in 24 hr. Modification of lysozyme with 2,4-pentanedione at pH 9 results in modification of 4 lysine residues and 4.5 arginine residues in 100 hr. Treatment of this modified protein with hydroxylamine regenerated the modified lysine residues but caused no change in the modified arginine residues. One arginine residue seems to be essential for the catalytic activity of the enzyme.
 ...
PMID:Modification of arginine and lysine in proteins with 2,4-pentanedione. 0 43

The dark and light reduction of nitrate and nitrite by cell-free preparations of the blue-green alga Anacystis nidulans has been investigated. The three following methods have been successfully applied to the preparation of active particulate fractions from the alga cells: (a) shaking with glass beads, (b) lysozyme treatment and lysis of the resulting protoplasts, and (c) sonication. The two enzymes of the nitrate-reducing system-namely, nitrate reductase and nitrite reductase-are firmly bound to the isolated pigment-containing particles, and can be easily solubilized by prolonging the vibration or sonication time. Both enzymes-whether solubilized or bound to the particles-depend on reduced ferredoxin as the immediate electron donor. In its presence, the alga particles catalyze the gradual photoreduction of nitrate to nitrite and ammonia, a process that can thus be considered as one of the most simple and relevant examples of Photosynthesis. Some of the properties of nitrate reductase have been studied. Nitrate reductase as well as nitrite reductase are adaptive enzymes repressed by ammonia.
 ...
PMID:Ferredoxin-dependent photosynthetic reduction of nitrate and nitrite by particles of Anacystis nidulans. 0 27

About 60 characteristics have been investigated in 7 hemolyzing and 12 nonhemolyzing strains of L. monocytogenes. From these investigations resulted inter alia that the organism grows well under strictly anaerobic conditions, esculin is split at 45 degrees C,NH3 is produced from peptone, but not from arginin, and H2S can be traced by sufficiently sensitive methods. All strains possess a lipase, muramidase, and deoxyribonuclease, the hemolytic ones only also a lecithinase. Besides, the hemolytic strains only dispose of experimental virulence and of a CAMP factor-like agent. The experimental animal of choice seems to be the conjunctivally infected guinea pig in which a generalized infection develops.
 ...
PMID:[Some properties of carrier strains of Listeria monocytogenes (author's transl)]. 81 65

Dicarboxylic amino acids constitute the most numerous residues of insoluble elastin in which are potentially ionizable in the physiological range of pH. These residues are essential in facilitating productive electrostatic interaction between elastase and elastin. The present study has investigated the possibility that the glutamic and aspartic acid residues of elastin are amidated. Acid-labile amide-bound ammonia of elastin was quantitated after hydrolysis of the insoluble protein with 2 M HC1 by incubating aliquots of microdistilled hydrolysates with glutamate dehydrogenase, excess alpha-ketoglutarate, and reduced nicotinamide adenine dinucleotide and measuring the resultant decrease in A340 due to oxidation of the dinucleotide cofactor. It was found that ligament elastin purified by repeated autoclaving contains approximately 2.29 mumol of acid-labile amide nitrogen per 10 mg of protein, a value equivalent to approximately 70% of the total number of dicarboxylic amino acid residues. Independent analysis of the amide content was obtained by amino acid analysis of an esterified and reduced elastin sample in which the free dicarboxylic amino acid residues had been converted to the corresponding alcohol derivatives. This analysis indicated that autoclaved ligament elastin contains approximately 18 glutamine, 3 asparagine, 4 glutamic acid and 5 aspartic acid residues per 1000 residues, in good agreement with the analysis of total acid-labile ammonia. The esterified and reduced elastin derivative was nearly inert as an elastase substrate, consistent with a lack of free dicarboxylic amino acid residues. However, addition of sodium dodecyl sulfate to this elastin derivative restores enzyme-substrate charge complementarity, and the elastin-ligand complex was readily hydrolyzed by elastase at the fully stimulated rate, emphasizing the control such ligands can exert in elastolysis. The amide bonds of elastin were found to be significantly more resistant to hydrolysis by 0.1 M NaOH at 98 degrees C than were those of lysozyme or free amidated amino acids. The finding that most of dicarboxylic amino acid residues of elastin exist at neutral amides further emphasizes the apolar character of elastin and has bearing upon the metabolic susceptibility, ligand-binding ability and structural aspects of this connective tissue protein.
 ...
PMID:Amidated carboxyl groups in elastin. 93 66

The authors studied the effect of some factors, including the conditions of preincubation, the action of 2-mercaptoethanol, EDTA, alpha-amylase, on protoplast production in four strains of Streptococcus lactis caused by lysozyme. The strains differed in the nisin-producing activity and in the structure of the cell walls that were not affected with lysozyme without either preincubation in 2-mercaptoethanol or in a salt medium with minimal inhibitory concentrations of DL-threonine. EDTA and alpha-amylase increased the lysozyme effect. Among seven buffer systems studied the most favourable for protoplast production in S. lactis is the ammonia-citric buffer with EDTA, and the best regeneration medium is the agar salt medium to which, depending on the strain, either glucose or sucrose should be added as a stabilizer.
 ...
PMID:[Various aspects of protoplast production in Streptococcus lactis]. 212 39

Ammonia-induced cell envelope injury was examined in pure cultures of Escherichia coli and Enterobacter aerogenes. Cell injury, as determined by the ratio of colony-forming units on m-T7 agar to colony-forming units on m-Endo agar, increased with exposure to increasing concentrations of ammonia. Cell envelopes appeared to be the site of injury as indicated by increasing susceptibility to lysozyme with increasing ammonia concentration. Cells exposed to ammonia also exhibited more cellular leakage than control cells. Leakage from cells exposed to ammonia included proteins, and all leaked substances increased in concentration as ammonia concentrations increased. The concentration of 2-keto-3-deoxyoctonate (KDO) in the outer membrane of E. coli increased with ammonia exposure, while KDO concentration in the outer membrane of E. aerogenes decreased. The results suggest that exposure of E. coli cells to high concentrations of ammonia disrupts the outer membrane and lipopolysaccharide-associated proteins, while E. aerogenes cells are affected through the disruption of bonds between KDO and the outer membrane.
 ...
PMID:Ammonia-induced cell envelope injury in Escherichia coli and Enterobacter aerogenes. 224 77

Measurements of ammonia release provide the first direct evidence that calmodulin becomes extensively deamidated during incubations at 37 degrees C, pH 7.4 or pH 11. A stoichiometry of 0.5 mol of NH3 released/mol of calmodulin is observed after 2 h at pH 11 or after 8-9 days at pH 7.4. These treatments also increase the ability of calmodulin to serve as a substrate for the isoaspartate-specific protein carboxyl methyltransferase from bovine brain. The stoichiometries of methylation are highly correlated with the stoichiometries of ammonia release. Deamidation and increased methyl-accepting capacity also occur in parallel for seven other proteins (aldolase, bovine serum albumin, cytochrome c, lysozyme, ovalbumin, ribonuclease A, and triosephosphate isomerase) upon incubation at pH 11. However, in comparison to calmodulin, these other proteins show very little deamidation and increased methylation capacity following incubation at pH 7.4. Deamidation of calmodulin at pH 7.4 is unaffected by the addition of 10(-7) M Ca2+; however, at 4 X 10(-6) M Ca2+, the rate of deamidation is inhibited by approximately 70%. The Ca2+-protection effect is consistent with the suggestion (B. A. Johnson, N. E. Freitag, and D. W. Aswad, (1985) J. Biol. Chem. 260, 10913-10916) that deamidation occurs preferentially at Asn-60 and/or Asn-97, each of which resides in a distinct Ca2+-binding domain.
 ...
PMID:Deamidation of calmodulin at neutral and alkaline pH: quantitative relationships between ammonia loss and the susceptibility of calmodulin to modification by protein carboxyl methyltransferase. 291 79

A method was developed for extracting enzymes from micro-organisms closely associated with ammonia-treated straw (NH3-S) that had been incubated in nylon bags in the rumen. Incubation of washed straw with 125 ml carbon tetrachloride/l and 20 micrograms lysozyme/ml for 3 h at 37 degrees gave carboxymethylcellulase (EC 3.2.1.4; CMCase) and NAD-linked glutamate dehydrogenase (EC 1.4.1.2; GDH) activities greater than those extracted by sonication. GDH associated with NH3-S increased with incubation time and was highest in sheep receiving a high-barley diet. Particle-bound CMCase activity reached a peak between 16 and 24 h and declined thereafter. Particle-bound GDH activity showed no correlation with dry matter (DM) degradation in the rumens of sheep fed on a range of diets. In contrast, CMCase activity after 24 h was highly correlated with DM degradability of the same samples at 24 h (r 0.98) and 48 h (r 0.94). It was concluded that GDH and CMCase can be used as indices of the total population of colonizing rumen micro-organisms and of the fibre-degrading population respectively, and that these enzymes can therefore be used to assess rapidly and with great sensitivity variations in the rumen environment that affect the rate of fibre breakdown.
 ...
PMID:Use of particle-bound microbial enzyme activity to predict the rate and extent of fibre degradation in the rumen. 303 99

In the cross-linking reaction of lysozyme between Leu129 (alpha-COO-) and Lys13 (epsilon-NH3+) using imidazole and 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC), a side reaction of the peptide bond inversion from alpha to beta between Asp101 and Gly102 was greatly reduced by addition of beta-(1,4)-linked trimer of N-acetyl-D-glucosamine [(NAG)3]. When methylamine or 2-hydroxyethylamine was further added, the extent of the cross-link formation was decreased and the derivative where the alpha-carboxyl group of Leu129 was modified with the amine was newly obtained. On the other hand, when ammonia was added, the beta-carboxyl group of Asp119 instead of the alpha-carboxyl group was mainly amidated. From these results, the presence of a salt bridge between Asp119 and Arg125 besides that between Lys13 and Leu129, is proposed. Enzymatic activities of the derivatives prepared here indicated that the modification of the alpha-carboxyl group reduced the activity to approximately 90% of that of native lysozyme. Des-Leu129 lysozyme, which lacks Leu129, also showed approximately 90% of the activity of native lysozyme. Therefore, the salt bridge between Lys13 and Leu129 may play some role in maintaining the active conformation of lysozyme.
 ...
PMID:Highly controlled carbodiimide reaction for the modification of lysozyme. Modification of Leu129 or Asp119. 350 4

For isosteric conversion of carboxyl groups of proteins into amide groups, ammonolysis of protein esters under mild conditions was attempted. Ammonolysis of methyl esters of lysozyme and bovine serum albumin proved to be incomplete. Highly reactive N-ethylsalicylamide esters of guanylated lysozyme were therefore prepared by subjecting the protein to reaction with N-ethylbenzisoxazolium ion at pH 4.2, 0 degree. Per molecule, 5-7 ester groups were introduced, with concomitant decrease of activity of 80-90%. Only 0.3 tyrosine was modified. On hydrolysis at pH 9.2 the activity was completely restored. At pH 7.9 three classes of ester groups could be distinguished: one group of high rate of hydrolysis (k1 = 1.5 min-1), three groups of intermediate rate (k2 = 0.13 min-1) and two groups of low rate (k3 = 0.018 min-1). The intermediate rate approximated the rate of hydrolysis of the model compound benzoylglycine N-ethylsalicylamide ester (k = 0.15 min-1). Ammonolysis at pH 9.2 in 2.0 M ammonia/ammonium acetate provided complete conversion of the ester groups into amide groups without restoration of activity, confirming the essentiality of certain carboxyl groups. In particular, rearrangement of the ester groups into relatively stable imide groups by O-N acyl migration was found to be completely absent. When native lysozyme was esterified with N-ethylbenzisoxazolium ion the activity did not completely return on hydrolysis.
 ...
PMID:Isosteric conversion of protein carboxyl groups into carboxamide groups. II. Application to lysozyme. 359 97


1 2 3 4 5 6 7 8 9 10 Next >>