Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human hepatoma (Hep G2) cells secrete nanogram quantities of carboxypeptidase enzymes which are capable of hydrolyzing COOH-terminal lysine and arginine residues. A carboxypeptidase with a neutral pH optimum (greater than pH 7.0) was partially purified from the conditioned medium and compared with pure plasma carboxypeptidase N. The two enzymes behaved in a similar manner on gel filtration (apparent Mr = 280,000), DE52 ion exchange chromatography, and concanavalin A-affinity chromatography and were indistinguishable enzymatically and immunologically. Immunoblots of the Hep G2 and plasma carboxypeptidase N before and following deglycosylation with peptide-N4-[N-acetyl-beta-glucosaminyl]asparagine amidase F revealed a similar, if not identical, multimeric structure. A second carboxypeptidase with a lower molecular weight and a pH optimum of 5.0 was also detected in the Hep G2 medium.
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PMID:Characterization of the carboxypeptidase N secreted by Hep G2 cells. 284 69

Characterization of the membrane receptor for the low density lipoproteins (LDL) has led to insights into cellular receptor physiology as well as mammalian lipid transport. Result with LDL have stimulated the search for specific receptors for other plasma lipoproteins. Receptors for high density lipoproteins (HDL) have been identified in human fibroblasts and smooth muscle cells. Specificity for this receptor has been difficult to define since normal HDL contains several apolipoproteins, and particles containing apolipoproteins B and E have been shown to compete for HDL binding. In the present study, we demonstrate that HDL isolated from a patient devoid of apolipoprotein E was bound specifically by human hepatic membranes. This binding reached saturation within 2 hours and was EDTA-resistant. Assuming a single receptor model, we found that 2.9 x 10(15) receptors/mg membrane protein bound with an affinity KD = 3.5 x 10(-7) M at 0 to 4 degrees C and KD = 1.9 x 10(-7) M at 37 degrees C. The binding was effectively competed with intact HDL3, with HDL3 that had undergone selective arginine and lysine residue modification, and with antibodies to apolipoproteins A-I and A-II. However, LDL, asialofetuin, and HDL3 which had undergone tyrosine modification by nitration, and anti-apolipoprotein B did not compete with apo A-I HDL binding. In contrast to LDL binding, the human hepatoma cell line, HEPG2, increased HDL binding with cholesterol loading that was specific for HDL3. Thus, hepatic tissue can modulate its recognition of HDL. Finally, hepatic membranes from a patient lacking normal hepatic LDL receptors bound apo A-I HDL normally. These data indicate that a saturable, specific regulatable receptor for apo E-free HDL is present in human liver.
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PMID:Characterization of a human hepatic receptor for high density lipoproteins. 298 87

The inhibitory effects of nicotinamide analogs on the activity of poly(ADP-ribose)) synthetase were compared to effects on precursor incorporation into macromolecules in three lines of hepatoma cells (Morris hepatomas 5123C, 7777 and HTC). N'-methylnicotinamide was a less effective inhibitor of poly (ADP-ribose) synthetase than was 1-methylnicotinamide while both these compounds had smaller inhibitory effects on the enzyme than were seen with nicotinamide or 3-aminobenzamide. On the other hand, the incorporation of [3H]thymidine into DNA and of [3H]uridine into RNA were inhibited by N'-methylnicotinamide in the concentration range 2-20 mM but not by 1-methylnicotinamide. Under the conditions examined there were no significant effects on the incorporation of [14C]lysine and [3H]leucine in hepatoma cells. The data indicated that the inhibitory effect of N'-methylnicotinamide on nucleic acid synthesis may be unrelated to action on poly (ADP-ribose) synthetase.
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PMID:Disparity in the effects of two N-methyl nicotinamides on poly(ADP-ribose) synthetase and macromolecular synthesis in hepatomas. 299 58

The catabolism of low-density lipoproteins (LDL), the major cholesterol-carrying lipoproteins in plasma, is mediated in part via a high-affinity uptake pathway in the liver. Non-enzymatic glucosylation of lysine residues of apolipoprotein B, the major protein of LDL, blocks receptor-mediated uptake of LDL by fibroblasts and endothelial cells. We investigated the effect of the degree of glucosylation on the binding, uptake and degradation of radioiodinated LDL by the human hepatoma cell line Hep G2. Human LDL was glucosylated with 250 mM glucose and 30 mM cyanoborohydride at 37 degrees C. Incubations ranging from 3 to 48 h in duration resulted in the formation of 6-27% of glucitol-lysine adducts as demonstrated by coincubation with [14C]glucose. The degree of glucose incorporation corresponded to the extent of inhibition of binding, uptake and degradation of LDL (10-90%). The data are consistent with the view that glucosylation of LDL markedly impairs their catabolism. This phenomenon may be related to the pathophysiology of the premature atherosclerosis observed in diabetes mellitus.
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PMID:Impaired hepatocyte binding, uptake and degradation of glucosylated low-density lipoproteins. 301 18

Rat liver cytosol has low hydrolytic activity against [3H]methylcasein at neutrality, but activity increases greatly on addition of various compounds such as poly-L-lysine, N-ethylmaleimide, and sodium dodecyl sulfate, suggesting that it contains latent proteolytic activity. The latent enzyme was found to be stabilized in the presence of 20% glycerol and to be activated by addition of poly-L-lysine. The latent enzyme was purified from a crude extract of rat liver to apparent homogeneity in the presence of 20% glycerol by conventional chromatographic techniques. The purified enzyme showed endoproteolytic activity toward various proteins when it was activated by the compounds listed above. It preferentially degraded N-substituted tripeptide substrates with a basic amino acid at the carboxyl terminus, as well as peptides containing neutral hydrophobic amino acids. It did not require activation for these peptidase activities, in contrast to its activity toward large proteins. Interestingly, a proteinase and a trypsin-like and a chymotrypsin-like peptidase activity could not be separated by customary chromatographic methods but were distinguishable by their sensitivities to various inhibitors, activators, and covalent modifiers, suggesting that the enzyme has three distinct active sites within a single protein. The enzyme seems to be a seryl endopeptidase showing maximal activity at neutral and weakly alkaline pH values. Thus, the enzyme is a unique protease with latent multifunctional catalytic sites. The distribution of the protease in soluble extracts of various rat tissues and cells was examined quantitatively by an enzyme immunoassay. The enzyme level was highest in liver and also in spleen, stomach, lung, small intestine, and kidney, but was low in heart, diaphragm, skeletal muscle, brain, and skin. The concentrations of enzyme in some established cell lines including hepatoma and rat kidney cells were comparable to that in normal liver hepatocytes. The enzyme was found mainly in the cytosol fraction, although a small amount was associated with microsomal membranes, suggesting that it is an extralysosomal protease. Immunohistochemical staining of the liver and skeletal muscles showed that the protease is distributed diffusely in panlobular hepatocytes with slight centrilobar predominance and is present in Kupffer cells, vascular endothelial cells, and bile duct epithelial cells in the liver and also diffusely in the intermyofibrillar spaces and vascular endothelial cells in skeletal muscle. The quantitative data obtained in the present study indicate the presence of the protease in the cytosol fraction of all rat tissues.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:A high molecular weight protease in the cytosol of rat liver. I. Purification, enzymological properties, and tissue distribution. 309 25

The transport of glycine and L-lysine into murine P388 leukemia cells has been examined. Glycine transport appears to be shared by both systems A and ASC in P388 cells. Glycine transport is Na+-dependent and is effectively blocked by alpha-(methylamino)isobutyric acid, threonine and alanine but only a marginal reduction in transport is seen with 100-fold excess cold 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid. System gly is not expressed in P388 cells. Lysine is largely transported by a Na+-independent, pH-insensitive system with a Km of 0.079 mM. Lysine transport is relatively unaffected by the addition of 100-fold excess cold alpha-(methylamino)isobutyric acid, 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid and the anionic amino acids, L-glutamate and L-aspartate. A partial inhibition of lysine transport was observed with L-threonine and L-leucine while L-arginine and L-histidine radically decreased lysine transport. Lysine appears to be transported by a system similar to the system y+ seen in cultured human fibroblasts, Ehrlich ascites cells, and hepatoma cell lines.
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PMID:Further studies on amino acid transport in murine P388 leukemia cells in vitro. Presence of system y+. 310 85

The rat core-specific lectin (CSL) or mannan-binding protein is synthesized and secreted by rat hepatocytes and H-4-II-E hepatoma cells. Prior to secretion proline and lysine residues with collagen-like sequences undergo hydroxylation and subsequent glycosylation of hydroxylysine to produce glucosylgalactosylhydroxylysine. Hydroxylation and subsequent glycosylation are inhibited by alpha,alpha'-dipyridyl (Colley, K. J., and Baenziger, U. U. (1987) J. Biol. Chem. 262, 10290-10295). We have used alpha,alpha'-dipyridyl to investigate the role of hydroxylation and glycosylation on interchain disulfide bond formation, assembly of subunits into high molecular weight complexes, attainment of carbohydrate and lipid binding ability, and secretion. Formation of disulfide-bonded dimers and trimers in the endoplasmic reticulum, assembly into high molecular weight complexes in the Golgi, and attainment of carbohydrate binding activity occur in either the presence or absence of these post-translational modifications. The mature fully processed form of the CSL binds hydrophobic matrices and is secreted at a slow, but linear, rate. Inhibition of proline and lysine hydroxylation and hydroxylysine glycosylation prevents CSL secretion and attainment of binding activity for hydrophobic matrices. Secretion of the lectin, although slow, appears to be an active process and may be related to the capacity to interact with membranes and/or lipids. Other proteins known to contain collagen-like sequences such as acetylcholinesterase, pulmonary surfactant apoproteins, and C1q also interact with lipids and/or membranes. The collagen-like domains of these proteins may also play a role in promoting such interactions.
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PMID:Post-translational modifications of the core-specific lectin. Relationship to assembly, ligand binding, and secretion. 311 40

Glycyl-histidyl-lysine (GHL) has been shown to have growth stimulatory effects on a number of different cell types including hepatocytes and hepatoma cells. In this study, the effects of GHL on Morris hepatoma 7777 cells were investigated. The greatest stimulatory effects on 3H-thymidine and 3H-leucine incorporation were observed at a GHL concentration of 2 ng/ml. In randomly proliferating cells, the incorporation of 3H-thymidine into DNA increased by 50% and that of 3H-leucine into protein by 29%. In addition, synergistic effects were observed when insulin and glucagon were included with GHL in the incubation mixture. Experiments with cells rendered quiescent by serum starvation indicated that cells in the G1 phase of the cell cycle are more sensitive to GHL stimulation. In these experiments, 3H-thymidine incorporation increased earlier and peaked at a higher value than in the control cells. This finding suggests that GHL may play a role in stimulating quiescent cells to re-enter the cell cycle.
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PMID:Effects of glycyl-histidyl-lysine on Morris hepatoma 7777 cells. 331 36

A glycophospholipid has been purified from rat liver membranes and shown to copurify with an insulin-sensitive glycophospholipid isolated from H35 hepatoma cells. The polar head group of this glycophospholipid is a phospho-oligosaccharide generated by treatment with phosphatidylinositol-specific phospholipase C from Staphylococcus aureus. It has been proposed that this phospho-oligosaccharide, which is also generated in response to insulin, may play a role in insulin action. Incubation of the catalytic subunit of cyclic AMP-dependent protein kinase with this phospho-oligosaccharide inhibited the activity of the kinase to phosphorylate histone IIA, a purified preparation of phospholipid methyltransferase and kemptide, a phosphate-accepting peptide. Inhibition of kinase activity was dose-dependent and 50% inhibition of histone phosphorylation was demonstrated with a concentration of phospho-oligosaccharide of around 2 microM. This effect was demonstrated in the presence of ATP at concentrations up to 1 mM, indicating that the phospho-oligosaccharide acts at physiological concentrations of ATP and that it does not compete with this nucleotide for the same binding site in the kinase. Inhibition by the phospho-oligosaccharide of kinase activity could be reversed by dilution or dialysis and was not reproduced by up to 50 microM myo-inositol, glucosamine, galactose, myo-inositol 1-phosphate, glucosamine 1-phosphate, galactose 1-phosphate or phosphorylcholine. The inhibitory activity was resistant to mild acid treatment but was labile to treatment with alkali, exposure to nitrous acid or incubation with sodium periodate. The phospho-oligosaccharide had no effect on the phosphorylation of lysine-rich histone by rat brain protein kinase C and on the binding of cyclic AMP to a cyclic AMP-dependent protein kinase. In conclusion, the data in this study suggested that a phospho-oligosaccharide generated from an insulin-sensitive glycophospholipid may play a role in insulin action by modulating cyclic AMP-dependent protein kinase activity.
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PMID:Inhibition of cyclic AMP-dependent protein kinase by the polar head group of an insulin-sensitive glycophospholipid. 333 45

Plasma levels of pipecolic acid, which is a minor metabolite of lysine, were determined by high-performance liquid chromatography in 22 patients with chronic liver disease, composed of 6 patients with chronic active hepatitis, 11 with liver cirrhosis and 5 with hepatocellular carcinoma. The plasma levels of pipecolic acid, when compared to those in normal subjects (1.00 +/- 0.08 nmoles per ml), were found to be significantly elevated (p less than 0.01) in patients with liver cirrhosis (1.93 +/- 0.24 nmoles per ml) and hepatocellular carcinoma (2.22 +/- 0.49 nmoles per ml), but did not show any significant change in patients with chronic active hepatitis. Plasma levels of pipecolic acid correlated positively with serum bile acid and bilirubin, and negatively with indocyanine green disappearance rate, cholinesterase and prothrombin time but not with plasma lysine levels. These results suggest that plasma levels of pipecolic acid increase almost parallel to the severity of liver damage, and that this increase in pipecolic acid may reflect the injury of liver peroxisomes which appear to be related to the degradation of pipecolic acid.
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PMID:Plasma levels of pipecolic acid in patients with chronic liver disease. 335 9


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