Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The localization of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase, E.C. 1.1.1.34) in the villous and crypt cells of the small intestine was accomplished after separating these cells from the mucosal layer by sequential dissociation in a "dual-buffer" system. Consistent separation was demonstrated by using the marker enzymes alkaline phosphatase, specific to the villous cell, and thymidine kinase, specific to the crypt cell. Cells obtained were 95-100% viable, and no relative difference in lability was observed, as evidenced by the equal distribution of acid phosphatase. This method of cell separation was an improvement over the "scraping" technique which damaged cells severely and produced villous preparations that contained little or no reductase activity. The HMG-CoA reductase specific activity in whole cell homogenates of the ileal villi was 0.47 and of the crypts was 0.27 nmol/min per mg of protein, considerably higher values than have been reported earlier. Also in comparison to the crypts, the villi incorporated 1.5-fold more [(14)C]-acetate into sterols, a ratio similar to that describing the distribution of HMG-CoA reductase in the two cell populations. These results unequivocally establish that the villi have higher HMG-CoA reductase activity than the crypts and confirm an earlier report from this laboratory that the villi are a major site of sterol synthesis. The sterol bio-synthetic capacity of the small intestine was highest in the ileum and decreased towards the jejunum. The HMG-CoA reductase specific activity of the ileum averaged 0.30 and that of the jejunum 0.10 nmol/min per mg of protein; however, the cholesterol content of the ileum was slightly lower than the jejunum. These results are discussed to suggest the possibility that the sterol content of the ileum may largely be due to in situ synthesis.
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PMID:3-Hydroxy-3-methylglutaryl coenzyme A reductase in isolated villous and crypt cells of the rat ileum. 92 17

The presence of lysosomal acid phosphatase (LAP) in coated pits at the plasma membrane was investigated by immunocytochemistry in thymidine kinase negative mouse L-cells (Ltk-) and baby hamster kidney (BHK) cells overexpressing human LAP (Ltk-LAP and BHK-LAP cells). Double immunogold labeling showed that at various stages of invaginating coated pits LAP colocalized with clathrin and plasma membrane adaptors (HA-2 adaptors). Quantitation of the immunogold label showed similar density of wild-type LAP in coated over non-coated areas of the plasma membrane, whereas an internalization-deficient, truncated mutant of LAP which lacks the cytoplasmic tail was less efficiently included into coated pits. Internalization of anti-LAP antibodies into endosomal vesicles was accompanied by rapid dissociation of the coat proteins as shown by an immunofluorescence assay. The role of clathrin-coated vesicles in internalization of LAP was further corroborated by microinjecting monoclonal antibodies against clathrin or HA-2 adaptors into BHK-LAP cells. Internalization of LAP as detected by an immunofluorescence assay was transiently blocked by microinjected antibodies against clathrin or HA-2 adaptors, whereas unrelated antibodies did not affect internalization. These data suggest that LAP is included into clathrin-coated pits of the plasma membrane for rapid internalization.
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PMID:Lysosomal acid phosphatase is internalized via clathrin-coated pits. 146 34

3-Hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.34), the major rate-limiting enzyme of cholesterogenesis, was studied in epithelial cells isolated in a villus to crypt gradient from chick duodenum, jejunum and ileum, in order to resolve the apparent controversy that exists on the anatomical localization of sterol synthesis in the intestine. Consistent separation was demonstrated by using the marker enzymes alkaline phosphatase, specific to the villus cells, and thymidine kinase, specific to the crypt cells. No relative difference in stability was observed, as shown by the equal distribution of acid phosphatase. Cells were 90-95 per cent viable. The highest specific activity of reductase was located in the microsomal fraction (41 per cent of the total). The mitochondria had lower specific activity (8 per cent of the total). The distribution of reductase activity in epithelial cells of the villus-crypt axis was also studied. The specific activity in each cell fraction from chick duodenum was clearly lower than that in jejunum and ileum. The jejunal and ileal crypt regions showed lower specific activity than the villus cells. About 70 per cent of total reductase activity was found in cells from the upper and the mid villus fraction in each intestinal segment.
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PMID:Distribution of 3-hydroxy-3-methylglutaryl-CoA reductase in isolated villus and crypt cells of chick duodenum, jejunum and ileum. 250 6

Resistance of human CCRF-CEM leukemic cells in tissue culture to 5-fluoro-2'-deoxyuridine (FdUrd) has been examined following a single drug exposure (FS sublines). In two FS sublines generated by soft agar cloning of FdUrd sensitive cells in the presence of 10 nM FdUrd, the level of drug resistance was maintained at 22- to 30-fold following 1 month growth in the absence of FdUrd. Characteristic of the FS sublines was a decreased accumulation and retention of free intracellular 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP) averaging 3% of FdUrd sensitive cells, a more rapid rate of disappearance of free FdUMP and FdUMP-bound thymidylate synthase (EC 2.1.1.45, 5,10-methylenetetrahydrofolate:dUMP C-methyltransferase), and enhanced alkaline and acid phosphatase activities. There was no significant difference in the number of nucleoside transport sites per cell among the FS sublines and FdUrd-sensitive cells, indicating that the decreased accumulation of FdUMP in the resistant sublines was not the result of impaired FdUrd transport across the plasma membrane. The more rapid turnover of FdUMP-bound TMP synthase observed in the FS sublines was neither accompanied by a decreased stability of the TMP synthase-FdUMP-5,10-methylenetetrahydrofolate ternary complex, nor an enhanced rate of degradation of FdUrd to the less potent agent, 5-fluorouracil. In addition, the growth rates of the two FS sublines were similar to that of FdUrd sensitive cells in medium containing hypoxanthine, methotrexate, and thymidine, indicating that there was no depletion of thymidine kinase (EC 2.7.1.21, ATP : thymidine-5'-phosphotransferase) in the FS sublines. Therefore, we propose that enhanced activities of acid and alkaline phosphatases, which influence the intracellular accumulation and retention of FdUMP, are important determinants of stable FdUrd resistance in CCRF-CEM cells.
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PMID:Resistance of CCRF-CEM cloned sublines to 5-fluorodeoxyuridine associated with enhanced phosphatase activities. 315 14

Some intestinal enZymes were assayed which were related to: (i) Cellular proliferation, for example, aspartate carbamoyltransferase, thymidine kinase, uridine kinase, and dihydroorotase; (ii) cellular differentiation, for example, lactase, invertase, maltase, alkaline phosphatase, and dipeptidase; and (iii) lysosomes, for example, beta-glucuronidase, acid beta-galactosidase, and acid phosphatase. These enzymatic determinations can be used to distinguish the crypt from the villus during healthy or diseased states.
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PMID:Intestinal enzymes: indicators of proliferation and differentiation in the jejunum. 431 2

PEG-mediated fusion between mouse Cl1d cells and primary Chinese hamster spleen cells produced interspecific hybrids which slowly and nonrandomly segregated Chinese hamster chromosomes. Cytogenetic and isozyme analysis (31 loci) of HAT and BrdU selected hybrid clones and subclones and of members of a hybrid clone panel retaining different combinations of Chinese hamster chromosomes enabled provisional assignment of the following enzyme loci on Chinese hamster chromosomes: thymidine kinase, galactokinase, and acid phosphatase-1 to chromosome 7; galactose-1-phosphate uridyltransferase to chromosome 2; and adenosine kinase, esterase D, glutathione reductase, glyoxalase, nucleoside phosphorylase, peptidases B and S, and phosphoglucomutase (PGM) 2 to chromosome 1. Assignments of PGM1, 6-phosphogluconate dehydrogenase, and enolase 1 to chromosome 2 were confirmed, and a chromosome 2 deletion (q23-q33) enabled the provisional assignment of PGM1 to that region. The assignments provide markers for the study of the genetic consequences of chromosomal rearrangements in Chinese hamster cell lines and support the concept of conservation of mammalian autosomal linkage groups.
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PMID:Confirmational, provisional, and/or regional assignment of 15 enzyme loci onto Chinese hamster autosomes 1, 2, and 7. 732 47

cis-Malonato-diammino platinum(II) significantly inhibited P-388 lymphocytic leukemia cell proliferation at 10 mg/kg/day. Incorporation studies showed that DNA synthesis was inhibited following in vivo drug therapy. The major inhibitory effects appeared to be on thymidine kinase and dihydrofolate reductase activities and on overall purine synthesis, with marginal effects on DNA polymerase and ribonucleotide reductase activities. In addition to the DNA inhibition, a marked increase in cyclic adenosine 3',5'-monophosphate levels was noted, which correlated with a rapid decrease in histone phosphorylation. Other minor effects of the drug included significant reduction of proteolytic activity, suppression of States 4 and 3 respiration, and an increase in adenosine triphosphatase and acid phosphatase activities of P-388 cells.
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PMID:Effects of cis-malonato-diammino platinum (II) on P-388 lymphocytic leukemia cell metabolism. 742 Feb 82

This chapter mainly deals with biochemical aspects on prostate specific antigen (PSA) and its clinical value. To a limited extent, also other tumor markers, which might be of importance in the evaluation of patients with prostate cancer are discussed. In serum, PSA exists in a free form or bound to antichymotrypsin. Interestingly, only 10% of PSA secreted from cancer cells seems to exist in a free form, as compared to 30% of PSA secreted from cells in benign prostatic hyperplasia (BPH). PSA seems to be closely, but not absolutely, related to tumor grade and stage. The mean value of PSA in patients with tumors dominated by Gleason grades 3 or below, was 10 ng/ml, compared to 29 ng/ml in those with higher grades. Patients with PSA values of 50 ng/ml or above almost exclusively had tumor of Gleason grades 4 or 5, and this limit usually reflected a generalized disease. Patients with PSA-values below 10 ng/ml almost exclusively had tumors confined to the prostate gland. In countries where screening for prostate cancer is believed in, it is important to understand that normal cut-off values are related to patient's age. The upper normal limit of males below 50 years of age should be set at 2.5 ng/ml, as compared to 6.5 ng/ml for men over 70 years of age. To improve the value of PSA determination and for scientific purposes, the standardization of the assay is urgently needed and under way. Prostate acid phosphatase (PAP) has in most centres been replaced by PSA. An elevated PAP value, as measured by the enzymatic method, invariably indicates a generalized disease and could thus be used as a complementary informative assay to PSA. Other markers have been used mainly to achieve additional prognostic information. In a multivariate analysis, the non-specific tumor marker neopterin, which reflects the host response to tumor antigens, was closely related to short-term prognosis. Neopterin was followed by thymidine kinase, a protein reflecting the cell turn-over and tumor grade. Also PSA at diagnosis seemed to add some prognostic information, whereas other markers did not.
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PMID:Tumor markers. Consensus Conference on Diagnosis and Prognostic Parameters in Localized Prostate Cancer. Stockholm, Sweden, May 12-13, 1993. 752 30

Biochemical markers of multiple myeloma (MM) including beta 2-microglobulin (beta 2MG), C-reactive protein, neopterin, fibronectin, lactate dehydrogenase (LDH), thymidine kinase, connective tissue components, osteocalcin, amylase, etc. are reviewed. To date, no reliable biochemical markers have been reported for the diagnosis of MM. beta 2MG and LDH are widely used to predict the prognosis of the patients with MM. The value of other parameters is however, controversial. The cytochemical diagnosis of MM, using acid phosphatase, beta-glucronidase and lysozyme are also mentioned. Furthermore, the significance of the assay of various hormones, ammonia, cobalamin and electrolytes in MM are discussed.
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PMID:[Biochemical markers of multiple myeloma]. 769 95

The clinical significance of plasma cell acid phosphatase (PCAP) was evaluated in 143 patients with monoclonal gammapathies, using a semiquantitative cytological scoring method. Significantly higher PCAP scores were measured in overt myelomas than in MGUS or in smouldering myelomas, during the phases of activity (diagnosis, progression, relapse), and in patients with extended disease. Among various clinical and laboratory parameters, PCAP was significantly related to the percentage of bone marrow plasma cells, the neoplastic growth fraction, as determined by Ki67 monoclonal antibody, and to serum levels of C-reactive protein. An inverse relationship was also found between PCAP and hemoglobin levels. Although the patients with "flaming" plasma cells exhibited low PCAP scores and poor prognosis, on the whole, myeloma patients with PCAP scores < 200 showed a significantly longer median overall survival than those with PCAP > 200 (46 vs 20 months, p < 0.003). However, in the multivariate analysis, beta 2-microglobulin, growth fraction, performance status, and serum levels of thymidine kinase and C-reactive protein, but not PCAP, maintained a significant prognostic relevance. In conclusion, although PCAP may be considered a marker of disease activity, other parameters provide better prognostic information in myeloma patients.
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PMID:Plasma cell acid phosphatase and prognosis in multiple myeloma. 781 11


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