Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of various glycolipids on the activity of immunoaffinity-purified calf thymus DNA polymerase alpha were studied in vitro. Preincubation with sialic acid-containing glycolipids, such as sialosylparagloboside (SPG), GM3, GM1, and GD1a, and sulfatide (cerebroside sulfate ester, CSE) dose-dependently inhibited the activity of DNA polymerase alpha, while other glycolipids, as well as free sphingosine and ceramide did not. About 50% inhibition was achieved by preincubating the enzyme with 2.5 microM of CSE, 50 microM of SPG or GM3, and 80 microM of GM1. Inhibition was noncompetitive with both the DNA template and the substrate dTTP, as well as with the other dNTPs. Since the inhibition was largely reversed by the addition of 0.05% Nonidet P40, these glycolipids may interact with the hydrophobic region of the enzyme protein. Apparently, the sulfate moiety in CSE and the sialic acid moiety in gangliosides were essential for the inhibition since neither neutral glycolipids (i.e., glucosylceramide, galactosylceramide, lactosylceramide) nor asialo-gangliosides (GA1 and GA2) showed any inhibitory effect. Furthermore, the ceramide backbone was also found to be necessary for maximal inhibition since the inhibition was largely abolished by substituting the lipid backbone with cholesterol. Increasing the number of sialic acid moieties per molecule further enhanced the inhibition, while elongating the sugar chain diminished it. It was clearly shown that the N-acetyl residue of the sialic acid moiety is particularly essential for inhibition by both SPG and GM3 because the loss of this residue or substitution with a glycolyl residue completely negated their inhibitory effect on DNA polymerase alpha activity.
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PMID:Sulfate- and sialic acid-containing glycolipids inhibit DNA polymerase alpha activity. 814 86

Carbohydrate tumor-antigens are important tumor markers for diagnosis and functional characteristics of human cancer cells. Detection of these carbohydrate tumor antigens on metastatic cancer cells in blood is a difficult task. We developed a highly sensitive method to detect a cell surface carbohydrate antigen using a hybrid technology referred to as cellular immuno-PCR. This technique uses the human monoclonal antibody (HumAb) L612, specific to a tumor-related antigen (ganglioside) GM3 that is expressed on the cell surface of human tumor cells and not normal cells. L612 coupled to a DNA oligonucleotide for exponential amplification by DNA polymerase chain reaction (PCR) can be used to enhance the detection signal. The DNA-HumAb conjugate was assessed for detection of a small number of human cancer cells after PCR amplification and Southern blot analysis. To assess the assay specificity human melanoma and other cancer cell lines, as well as healthy donor and melanoma patients, bloods were assessed. Cellular immuno-PCR requires < 1 ng/ml DNA-HumAb complex and was shown to have a detection level of < 10 cells in titration studies in which melanoma cells were diluted in 2 million healthy donor peripheral blood lymphocytes. The assay was shown to be very sensitive and could detect low levels of GM3 antigen expression by tumor cells. This novel approach for detecting a carbohydrate tumor antigen on tumor cells in blood provides a potential useful clinicopathological assay.
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PMID:Cellular immuno-PCR. Detection of a carbohydrate tumor marker. 962 47