Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Regulation of cell growth and metabolism by protein tyrosine phosphorylation involves dephosphorylation via the action of protein tyrosine phosphatases (PTPases). We have characterized the membrane PTPases in rat liver, monitoring their activity by measuring the dephosphorylation of P-Tyr-reduced, carboxyamidomethylated and maleylated lysozyme (P-Tyr-RCML) and P-Tyr-myelin basic protein (P-Tyr-MBP). Separation of membrane PTPases by poly (L-lysine) chromatography yielded three peaks of PTPase, termed I, II and III. PTPases I and II were most active with P-Tyr-RCML, whereas PTPase III showed greater activity with P-Tyr-MBP than with P-Tyr-RCML (ratio of activities 4:1). Separation of membrane proteins by gel-filtration chromatography yielded two peaks of activity. Based on substrate specificity, sensitivity to inhibitors and requirement for thiol-containing compounds, the activity peak with an Mr of approximately 400,000 corresponded to PTPase III, whereas that with an Mr of approx. 40,000 contained PTPases I and II. All three PTPases dephosphorylated epidermal growth factor receptors and insulin receptors, but only PTPases I and II were active with P-Tyr-asialoglycoprotein receptors. Although none of the above characteristics distinguished between PTPases I and II, only PTPase I reacted in a Western immunoblotting procedure with anti-peptide antibodies directed towards human placental PTPase. We conclude that the membrane fraction from rat liver contains at least three distinct PTPases.
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PMID:Hepatic protein tyrosine phosphatases in the rat. 184 53

L-Canavanine is incorporated into the lysozyme synthesized, in response to administration of bacterial cell wall materials, by canavanine-treated larvae of the tobacco hornworm Manduca sexta (Sphingidae). Maximum canavanine incorporation into M. sexta lysozyme occurs when the larvae are provided 1 mg of canavanine g-1 fresh body weight. Analysis of canavanine-containing lysozyme purified from these insects reveals that 21% of the arginine residues are replaced by canavanine; this residue substitution results in a loss of 49.5% of the catalytic activity. When the larvae are provided 0.5 mg of canavanine g-1, 16.5% of the arginine residues are substituted by canavanine and 39.5% of the catalytic activity is lost. Canavanine is also incorporated into the lysozyme induced by canavanine-treated pupae of the giant silk moth Hyalophora cecropia (Saturnidae). In contrast, replacement of 17% of the arginine in H. cecropia lysozyme by canavanine fails to affect the catalytic activity. We have determined the primary structure of M. sexta lysozyme and compared it with the primary structure of H. cecropia lysozyme which has been described elsewhere. M. sexta lysozyme has an arginine at positions 23, 42, and 107. H. cecropia contains serine, lysine, and lysine, respectively, at these locations. The ability of incorporated canavanine to inhibit M. sexta lysozyme activity selectively may result from the fact that replacement of any one of the 3 arginine residues at position 23, 42, or 107 by canavanine causes the loss of catalytic activity.
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PMID:Studies of L-canavanine incorporation into insectan lysozyme. 187 26

A fluorescent compound has been detected in proteins browned during Maillard reactions with glucose in vitro and shown to be identical to pentosidine, a pentose-derived fluorescent cross-link formed between arginine and lysine residues in collagen (Sell, D. R., and Monnier, V. M. (1989) J. Biol. Chem. 264, 21597-21602). Pentosidine was the major fluorophore formed during nonenzymatic browning of ribonuclease and lysozyme by glucose, but accounted for less than 1% of non-disulfide cross-links in protein dimers formed during the reaction. Pentosidine was formed in greatest yields in reactions of pentoses with lysine and arginine in model systems but was also formed from glucose, fructose, ascorbate, Amadori compounds, 3-deoxyglucosone, and other sugars. Pentosidine was not formed from peroxidized polyunsaturated fatty acids or malondialdehyde. Its formation from carbohydrates was inhibited under nitrogen or anaerobic conditions and by aminoguanidine, an inhibitor of advanced glycation and browning reactions. Pentosidine was detected in human lens proteins, where its concentration increased gradually with age, but it did not exceed trace concentrations (less than or equal to 5 mumol/mol lysine), even in the 80-year-old lens. Although its precise carbohydrate source in vivo is uncertain and it is present in only trace concentrations in tissue proteins, pentosidine appears to be a useful biomarker for assessing cumulative damage to proteins by nonenzymatic browning reactions with carbohydrates.
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PMID:Formation of pentosidine during nonenzymatic browning of proteins by glucose. Identification of glucose and other carbohydrates as possible precursors of pentosidine in vivo. 190 67

When assayed in vitro, the activity of the photosynthetic enzyme ribulose 1,5 bisphosphate carboxylase oxygenase is both enhanced and protected from spontaneous decay by exogenous proteins such as hemoglobin, serum albumin, and aldolase. Other proteins and amino acids tested are either ineffective (lysozyme, ferritin, lysine, and cysteine) or afford only partial protection (catalase, glycine, and phenylalanine). Protective proteins do not bind to, or exchange disulfides with, ribulose 1.5 bisphosphate carboxylase/oxygenase. Since their effect can be mimicked by reductively treated detergents such as Triton X-100, it appears that proteins protect from decay by quenching the spontaneous oxidative degradation and inhibiting surface adsorption which could lead to enzyme unfolding. Release of adsorbed molecules from the container surface is likely to be the cause of carboxylase activity enhancement.
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PMID:Protection and enhancement of ribulose 1,5 bisphosphate carboxylase activity by exogenous proteins. 191 Apr 60

The mechanism of reaction of proteins with 3-hydroxyanthranilic acid (3OHA) under oxidizing conditions has been examined. A range of proteins were found to tan when exposed to oxidized 3OHA. One exception was lysozyme which tanned only after being denatured by reduction and carboxymethylation. Chemical modification experiments using bovine serum albumin (BSA) suggested that lysine was the primary site of reaction in 3OHA-mediated protein tanning. This reactivity of 3OHA toward lysine was confirmed by autoxidizing 3OHA in the presence of amino acid homopolymers. The rate of modification of both BSA and polylysine was pH dependent. At neutral pH, a component of the coloration of the protein was found to be due to the formation of a lysyl-p-quinone adduct. Other products appear to arise through addition to the 3OHA quinone imine. Poly-(Glu,Lys) was tanned by 3OHA at a greatly reduced rate, suggesting that electrostatic interactions may influence the reaction with lysine residues and may provide an explanation for the lack of tanning of lysozyme. Despite the reaction between 3OHA and lysine, amino acid analysis revealed little quantitative change in the lysine content of proteins even after exposure to 3OHA for a period of 24 h. These results support the proposal that reaction with lysine residues is the major route of protein tanning by 3-hydroxyanthranilic acid.
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PMID:Modification of proteins by 3-hydroxyanthranilic acid: the role of lysine residues. 192 12

The formation of acceptor for the N epsilon-(D-Ala)-acceptor transpeptidase is an essential feature of nascent peptidoglycan processing. In Gaffkya homari the synthesis of cross-bridges in peptidoglycan includes a variety of penicillin-sensitive enzymes, e.g., transpeptidase, DD-carboxypeptidase, and LD-carboxypeptidase. To determine the primary target, we grew cultures in the presence of the MICs of benzylpenicillin (0.2 microgram/ml), methicillin (10 micrograms/ml), cephalothin (5 micrograms/ml), and cefoxitin (25 micrograms/ml) and examined the monomer-dimer composition of each peptidoglycan by high-performance liquid chromatography after muramidase digestion. From these studies it was recognized that of all the dimers, the synthesis of the predominant cross-bridge, diamidated octapeptide (-Ala-iso-D-Gln-Lys-D-Ala -Ala-iso-D-Gln-Lys-D-Ala), is most sensitive to the action of the beta-lactam at its MIC. The enhanced deamidation of the acceptor tetrapeptide, one of the substrates for the transpeptidase, is correlated with the inhibition of this cross-bridge. For example, at the MIC of benzylpenicillin, the ratio of amidated tetrapeptide to nonamidated tetrapeptide decreased from 2.8 in the control to 1.0 in the treated culture. From these results it would appear that a decrease in preferred acceptor for the transpeptidase results in the inhibition of synthesis of this major cross-bridge. Thus, the metabolism of the amide function of the monomer peptides may represent an additional feature of processing in the assembly of cross-bridged dimers in the peptidoglycan of this organism that is sensitive to the action of beta-lactam.
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PMID:Biosynthesis of peptidoglycan in Gaffkya homari: on the target(s) of benzylpenicillin. 195 43

Several previous findings have suggested that the cationic nature of lysozyme is a major factor in its bactericidal activity. Since a number of cationic proteins or peptides have been reported to cause membrane damage in bacteria, we investigated the effect of lysozyme on glucose fermentation and intracellular pH and K+ in Streptococcus mutans under conditions in which lysis does not occur. Results showed that lysozyme and poly-D-lysine (PDL) cause inhibition of glucose fermentation at pH 5.5 in a dose-dependent manner. Human placental lysozyme and hen egg-white lysozyme exhibited similar inhibitory potency on glucose fermentation. Both lysozyme and PDL caused a marked acidification of the cytoplasm of S. mutans. However, when cytoplasmic pH was examined as a function of fermentation rate, the relationship was similar regardless of the presence or absence of lysozyme or PDL. Therefore, acidification of the cytoplasm appeared to not depend specifically on lysozyme or PDL. In contrast, the same relationship between the profound loss of intracellular K+, when fermenting cells were exposed to either lysozyme or PDL, and the fermentation rate was not exhibited in the controls. These results indicate that lysozyme and PDL specifically affected the ability of the cells to maintain intracellular K+. We concluded that lysozyme and PDL indeed perturb membrane function, perhaps in a selective manner. Furthermore, the similarity in action of lysozyme and the cationic homopolypeptide PDL supports the notion that the cationic property of lysozyme indeed plays a significant role in its antibacterial activity.
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PMID:Effect of lysozyme on glucose fermentation, cytoplasmic pH, and intracellular potassium concentrations in Streptococcus mutans 10449. 198 80

In a previous report from this laboratory (N. J. Laible and G. R. Germaine, Infect. Immun. 48:720-728, 1985), evidence was presented to suggest that the bactericidal actions of both reduced (i.e., muramidase-inactive) human placental lysozyme and the synthetic cationic homopolymer poly-D-lysine involved the activation of a bacterial endogenous activity that was inhibitable by N,N',N"-triacetylchitotriose (chitotriose). In the present investigation however, we found that the bactericidal and bacteriolytic action of poly-D-lysine could be prevented only by some commercially available chitotriose preparations and not by others. Analysis by physical and chemical methods failed to distinguish protective chitotriose (CTa) and nonprotective chitotriose (CTi) preparations. CTi and CTa preparations displayed equal capacities to competitively inhibit binding of [3H]chitotriose by immobilized lysozyme and were indistinguishable in their abilities to block the lytic activity of lysozyme against Micrococcus lysodeikticus cells. Elemental analysis revealed significantly higher levels of phosphorus, calcium, iron, sodium, manganese, and copper in CTa. Removal of metals from CTa by chelate chromatography completely abolished the poly-D-lysine-protective capacity. Of the metals detected, only ferric iron (5 to 10 microM) mimicked the protective action of CTa. A Fe(III) concentration of 50 microM was required to inhibit lysozyme (5 micrograms/ml). Both Fe(III) and CTa (but not CTi) quantitatively blocked the labeling of poly-D-lysine by fluorescamine, suggesting that the primary amino groups of the lysine residues participate in iron binding. Thus, it appears that the poly-D-lysine-protective capacity of certain chitotriose preparations was due not to the chitotriose itself but to contaminating metal ions which interact directly with the polycationic agent. In contrast, Fe(III) cannot account for inhibition of either the bactericidal or bacteriolytic activity of lysozyme by chitotriose.
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PMID:Inhibition of bactericidal and bacteriolytic activities of poly-D-lysine and lysozyme by chitotriose and ferric iron. 198 82

The lysis gene region of phage 21 contains three overlapping reading frames, designated S21, R21, and Rz21 on the basis of the analogy with the SRRz gene cluster of phage lambda. The 71-codon S21 gene complements lambda Sam7 for lysis function but shows no detectable homology with S lambda in the amino acid or nucleotide sequence. A highly related DNA sequence from the bacteriophage PA-2 was found by computer search of the GenBank data base. Correction of this sequence by insertion of a single base revealed another 71-codon reading frame, which is accordingly designated the SPA-2 gene and is 85% identical to S21. There are thus two unrelated classes of S genes; class I, consisting of the homologous 107-codon S lambda and 108-codon P22 gene 13, and class II, consisting of the 71-codon S21 and SPA-2 genes. The codon sequence Met-Lys-(X)-Met...begins all four genes. The two Met codons in S lambda and 13 have been shown to serve as translational starts for distinct polypeptide products which have opposing functions: the shorter polypeptide serves as the lethal lysis effector, whereas the longer polypeptide acts as a lysis inhibitor. To test whether this same system exists in the class II S genes, the Met-I and Met-4 codons of S21 were altered in inducible plasmid clones and the resultant lysis profiles were monitored. Elimination of the Met-1 start results in increased toxicity, and lysis, although not complete, begins earlier, which suggests that both starts are used in the scheduling of lysis by S21 and is consistent with the idea that the 71- and 68-residue products act as a lysis inhibitor and a lysis effector, respectively. In addition, the R gene of 21 was shown to be related to P22 gene 19, which encodes a true lysozyme activity, and was also found to be nearly identical to PA-2 ORF2. We infer that the 21 and PA-2 R genes both encode lysozymes in the T4 e gene family. These three genes form a second class lambdoid R genes, with the lambda R gene being the sole member of the first class. The existence of two interchangeable but unrelated classes of S genes and R genes is discussed in terms of a model of bacteriophage evolution in which the individual gene is the unit of evolution.
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PMID:Dual start motif in two lambdoid S genes unrelated to lambda S. 201 62

We used the heat denaturation of lysozyme to induce the in vitro formation of protein deposits on 60 poly-HEMA contact lenses (38.6% water). Each lens was individually placed in 20 mL of a 0.04% lysozyme solution. The lenses were divided into two equal groups. In the first group (30 lenses), bendazac lysine (100 mg) was added to the lysozyme solution. The second group of lenses was used as control. Quantitative analysis of protein deposits on the lenses of both groups was carried out by a colorimetric test. In the lenses where deposit formation occurred in the presence of bendazac lysine, a mean protein level of 7.17 +/- 3.42 micrograms per lens was found; in the control group the mean value was 30.6 +/- 8.22 micrograms per lens. Student's t-test showed this difference to be significant (P less than 0.001).
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PMID:Use of bendazac lysine to limit protein deposition on soft contact lenses in vitro. 204 21


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