Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0272170 (SDS)
 50,377 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

L-Lysine-alpha-ketoglutarate reductase (N5-(1,3-dicarboxypropyl)-L-lysine: NADP+ oxidoreductase (L-lysine-forming, EC 1.5.1.8) was purified from rat liver mitochondria to a homogeneous state judged by SDS polyacrylamide gel electrophoresis, and its molecular weight was estimated as 52000. On Sepharose 4B filtration it has a molecular weight of 230 000 and it is suggested that the active enzyme is a tetramer of subunits of similar size. The purified enzyme was clearly separated from saccharopine dehydrogenase (N5-(1,3-dicarboxypropyl)-L-lysine:NAD+ oxidoreductase (L-glutamate-forming, EC 1.5.1.9). The reactions of purified L-lysine-alpha-ketoglutarate reductase favored the forward reaction (saccharopine formation) and the rate of the reverse reaction (lysine formation) was only 3--5% that of the forward reaction. The forward reaction was specific for L-lysine, alpha-ketoglutarate and NADPH and followed Michaelis-Menten kinetics, whereas the dose vs. response curve of the reverse reaction was sigmoidal with saccharopine. Among the amino acids examined, ornithine, leucine and tryptophan inhibited the forward reaction competitively. These results are different from earlier reports on human and yeast enzymes. The fact that rats fed on lysine-deficient diet do not lose weight much is discussed in relation to the properties of this enzyme.
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PMID:Purification and properties of L-lysine-alpha-ketoglutarate reductase from rat liver mitochondria. 68 35

Cytokinin binding protein was isolated and purified from tobacco leaves by bioaffinity chromatography on a Sepharose column on which benzyladenine (BA), synthetic cytokinin, had been introduced as an affinity ligand by the cyanogen bromide method. The purified protein bound specifically to cytokinins; its binding was inhibited remarkably by the addition of BA and kinetin and slightly by adenine, but not by adenosine in vitro. The dissociation constant, Kd, of the protein-BA complex was about 4 x 10(-5)M. The profiles of SDS polyacrylamide gel electrophoresis and gel filtration indicate that the protein consisted of a single polypeptide chain. Amino acid analysis showed that the protein contained 4 basic, 6 acidic, and 25 neutral amino acids but lacked tryptophan. The molecular weight of the protein was determined to be about 4,000 to 5,000 daltons by gel filtration, SDS polyacrylamide gel electrophoresis and amino acid analysis. The coupling conditions of BA to Sepharose by the cyanogen bromide method are described and discussed.
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PMID:Isolation of cytokinin binding protein from tobacco leaves by bioaffinity chromatography and its partial characterization. 86 70

The trypsin inhibitor in eggplant, Solanum melongena L., was isolated and purified by the improved method with the techniques of dialysis using acetylated cellulose tube and ion-exchange chromatography on DEAE-Sephadex. The final preparation was found to be homogeneous by disc and SDS-polyacrylamide gel electrophoresis. This inhibitor had the molecular weight of about 6,200, the pI value of 4.7, and furthermore characteristic amino acid composition lacking in tryptophan, histidine, valine and methionine. The trypsin inhibition data indicated that the purified inhibitor combined with bovine trypsin [EC 3.4.21.4] in the molar ratio of 1:1. These properties of this inhibitor were in agreement with those of the dialyzable eggplant trypsin inhibitor previously purified, indicating that the dialyzable and non-dialyzable inhibitors in eggplant are identical.
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PMID:An improved method for the purification of eggplant trypsin inhibitor. 87 80

In quiescent human fibroblasts stimulated to proliferate by fresh medium plus 15% serum, no changes were seen in the incorporation of 3H tryptophan into the protein of nuclear ribonucleoprotein during the first three hours following re-feeding. This was in contrast to non-histone chromosomal proteins where the incorporation increased by 90% within ten minutes. The density of the formaldehyde fixed nuclear ribonucleoprotein in CsCl was 1.43-1.44 g/ml and this also did not change following stimulation. The electrophoretic profile of the proteins of nuclear ribonucleoprotein on SDS gels exhibited a predominant band corresponding to a molecular weight of 44,000 closely trailed by a band at 47,000 and other bands at higher molecular weight. This pattern was not altered by serum stimulation and the same was true for the more complex electrophoretic profile of the chromatin proteins. Following a 10-minute pulse of 3H-tryptophan at ten minutes after stimulation, there was a selective increase in the labeling of non-histone chromosomal protein of molecular weight 59,000; no change was seen in the labeling of any protein of nuclear ribonucleoprotein.
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PMID:Serum stimulation of human fibroblasts: effect on non-histones of nuclear ribonucleoprotein and chromatin. 89 30

Low molecular weight components (g1, g2, and g3) were isolated from rabbit skeletal muscle myosin and their amino acid compositions were analyzed. One mole tryptophan was found in g1 and in g2, but none in g3. One mole of acetic acid was found per mole of each g-chain and it was concluded that the N-terminal groups of all three g-chains are acetylated. The minimum molecular weight of the g-chains were estimated from their amino acid compositions. It was estimated by SDS-disc electrophoresis that 1 mole of myosin contained 0.90, 1.7, and 0.63 moles of g1, g2, and g3, respectively. Similar values were obtained with psoas muscle myosin, but in heavy meromyosin prepared from skeletal muscle myosin the content of g2 was much lower, and that of g3 was much higher.
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PMID:Low molecular weight components (g-chains) of myosin from rabbit skeletal muscle. Separation, amino acid compositions and contents in myosin. 112 22

The site-specific lysozyme damage by iron and by iron-catalysed oxygen radicals was investigated. A solution of purified lysozyme was inactivated by Fe(II) at pH 7.4 in phosphate buffer, as tested on cleavage of Micrococcus lysodeikticus cells; this inactivation was time- and iron concentration-dependent and was associated with a loss of tryptophan fluorescence. In addition, it was reversible at pH 4, as demonstrated by lysozyme reactivation and by the intensity of the 14.4-kD-band on SDS-PAGE. Desferal (1 mM) and Detapac (1 mM) added before iron, prevented lysozyme inactivation, while catalase (100 micrograms/ml), superoxide dismutase (100 micrograms/ml) and bovine serum albumin (100 micrograms/ml) gave about 30 to 40% protection by competing with lysozyme for iron binding. The denaturing effect of iron on lysozyme was studied in the presence of H2O2 (1 mM) and ascorbate (1 mM); under these conditions the enzyme underwent partly irreversible inactivation and degradation different to that produced by gamma radiolysis-generated .OH. Catalase almost fully protected lysozyme; in contrast, mannitol (10 mM), benzoate (10 mM), and formate (10 mM) provided no protection because of their inability to access the site at which damaging species are generated. In this system, radical species were formed in a site-specific manner, and they reacted essentially with lysozyme at the site of their formation, causing inactivation and degradation differently than the hydroxyl radical.
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PMID:Mechanism of lysozyme inactivation and degradation by iron. 133 14

1. An arginine ester hydrolase was isolated from Heloderma horridum (beaded lizard) venom by Sephadex G-75, DEAE-Sephacel and Q-Sepharose column chromatography, resulting in 5.4 mg of purified enzyme from 320.0 mg of crude venom. 2. The enzyme was shown to be homogeneous by both SDS and non-SDS disc electrophoresis on polyacrylamide gel at pH 8.3. 3. The enzyme possesses arginine ester hydrolase and transglutaminase-like activities, but did not exhibit clotting activity. 4. Molecular weight was determined to be ca 29 kDa, with an isoelectric point of 4.4. 5. The enzyme was stable to heat treatment (95 degrees C, 10 min) and to pH changes over the range 2-11. 6. The arginine ester hydrolase was inactivated by diisopropylfluorophosphate (DFP), beta-mercaptoethanol and N-bromosuccinimide, suggesting that serine, disulfide bonds and tryptophan are involved in enzymatic activity. 7. Amino terminal sequences were determined and appear to be similar to porcine pancreatic kallikrein.
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PMID:Isolation and characterization of arginine ester hydrolase from Heloderma horridum (beaded lizard) venom. 134 36

CheR methyltransferase from Salmonella typhimurium was directly photolabeled with S-adenosyl-L-[methyl-3H]methionine. The labeled protein was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and then was detected by fluorography. The methylase-S-adenosyl-L-methionine adduct was found to be stable under the experimental conditions employed. Labeling was found to be a function of the concentration of enzyme, S-adenosyl-L-methionine (AdoMet), and the intensity and time of UV irradiation. The extent of labeling and protein methylation was found to be inhibited by S-adenosyl-L-homocysteine, S-adenosyl-L-ethionine, and sinefungin, which are known to compete with AdoMet for the same binding site on the enzyme. Our earlier data showed that the enzyme has 2 cysteine residues and that these are important for enzyme activity. Here, we show that sulfhydryl reagents inhibit the photolabeling of the substrate to the enzyme, indicating the presence of cysteine in the vicinity of the substrate-binding site. We also found that when Cys31 was modified to Ser, no photolabeling of CheR was observed, whereas a modification of Cys229 to Ser had little effect on the ability of AdoMet to label the enzyme. This suggests that Cys31 is located at or near AdoMet-binding site. The labeled protein was cleaved at tryptophan residues, generating two major fragments, each containing 1 cysteine residue. SDS-PAGE and fluorography of the cleaved products indicated the presence of the label being associated with the Cys31 fragment. Similar results were obtained when the labeled protein was cleaved at glutamic acid residues using V8 protease. A tryptic digest of the labeled protein showed two radioactive peptide peaks when subjected to separation on reverse phase high pressure liquid chromatography. The labeled peptides were further digested to free amino acids, and the labeled amino acid was identified as S-methylcysteine by thin layer chromatography. These results indicate that Cys31 may be involved with substrate binding, as well as with catalysis.
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PMID:Photolabeling of CheR methyltransferase with S-adenosyl-L-methionine (AdoMet). Studies on the AdoMet binding site. 134 19

The ultraviolet B-induced destruction of tryptophan residues and lipid peroxidation of high-density lipoproteins is accompanied by the immediate and marked structural modification of the apolipoproteins, as revealed by SDS-polyacrylamide gel electrophoresis and immunoblot with specific monoclonal antibodies. Formation of several polymers of apolipoprotein A-I, apolipoprotein A-II or both apolipoproteins occurred, although apolipoprotein A-II did not contain any Trp residue. These results suggest that initial photochemical damage can be transferred via intramacromolecular processes to other sites within the same apolipoprotein and by intermacromolecular reactions from apolipoprotein A-I to other apolipoproteins. In both cases, lipid peroxidation enhances the propagation of the initial photochemical damage. The physiological significance of this work is discussed with respect to the low-light doses required for the alterations of the high-density lipoproteins.
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PMID:Modified apolipoprotein pattern after irradiation of human high-density lipoproteins by ultraviolet B. 142 Feb 87

Changes occurring at the membrane are believed to be the decisive factors in the initiation of diabetic cataract. During diabetic hyperglycemia lens crystallins were shown to undergo glycation. Several studies indicated that glycation brings about protein conformational changes thus implicated in cataractogenesis. Since the membrane proteins are the first targets for glycation, in this study we measured the glycation of alkali washed urea-insoluble membrane proteins from control and diabetic rats by two different methods, phenyl-boronate affinity chromatography and [3H]NaBH4 reduction, and confirmed by amino acid analysis. There was a significant increase in the glycation of membrane proteins in diabetic cataract lenses when compared to controls. It appears that lysine is the major site of glycation. Concomitant to early glycation, there was an increase in non-tryptophan fluorescence (Ex: 350 nm/Em: 440 nm) in the diabetic lens membrane proteins suggesting the presence of advanced glycation mediated protein cross-links. In order to identify whether the major membrane intrinsic protein, MIP26, undergoes glycation, we isolated MIP26 along with its degradatory product MIP22 as one peak on molecular sieve HPLC. HPLC isolated MIP26/MIP22 was further separated on SDS-PAGE followed by slicing and counting. This analysis revealed that MIP26 and MIP22 were more or less equally glycated in controls, however, in diabetic rats glycation of MIP22 was glycated slightly higher than MIP26. Moreover, the proportion of MIP22 increased by about 2-fold in diabetic lenses compared to controls. Thus it appears that major glycation sites are still retained in MIP22 in diabetic rat lenses. In vitro glycation studies with bovine lens membranes were also done using 14C glucose, followed by SDS-PAGE and autoradiography. The major protein glycated in vitro also seems to be MIP26. Interestingly, MIP22 was less glycated than MIP26 in vitro.
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PMID:Glycation of lens membrane intrinsic proteins. 142 26


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