Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation and integration of purine nucleotide biosynthesis is considered from the viewpoint of the main groups of reaction sequences involved and with respect to some specific organs and tissues. Inhibiting either IMP dehydrogenase or adenylosuccinate synthetase in rat liver in vitro reduced the rate of purine do novo synthesis with respect to the purine remaining in the tissue and did not materially affect the rate with respect to the purines extruded into the incubation medium. These results are considered in contrast to the results of previous studies in cultured lymphoblasts. The relative activities of purine de novo synthesis and of purine salvage have been assessed in different tissues by the activities of amidophosphoribosyltransferase and hypoxanthine phosphoribosyltransferase (HPRT), respectively. Changes in purine de novo synthesis as measured by [14C]formate incorporation into cellular purines were reflected in the amidophosphoribosyltransferase activities. The capacity of different tissues to synthesize purines de novo is widespread and the role of the liver as the main site of purine de novo synthesis in vivo and exporting purines to other tissues appears questionable. Regulatory mechanisms may well be tissue specific. The age-related changes in the activity of the purine de novo synthesis and purine salvage pathways, respectively, in the brain suggest that it is physiological or neuropharmacological functions of the developed brain rather than cell division and organogenesis which require a high level of purine salvage relative to purine de novo synthesis. This is compatible with the observation that purine de novo synthesis alone can meet the needs for additional purine nucleotides which lectin induced lymphocyte transformation involves. The mechanism whereby purine de novo synthesis is initiated during lectin induced lymphoblast transformation remains obscure.
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PMID:Some regulatory and integrative aspects of purine nucleotide biosynthesis and its control: an overview. 615 30

To study human T cell suppression of immunoglobulin (Ig) synthesis with homogeneous populations of immunoregulatory cells, human suppressor T cell hybridomas were prepared by somatic cell fusion of concanavalin A-activated peripheral blood T cells with hypoxanthine-guanine phosphoribosyltransferase-(HGPRT, EC 2.4.2.8) deficient human leukemic CEM T cells. After selection in hypoxanthine-aminopterin-thymidine (HAT) medium and cloning by limiting cell dilution, two human T cell hybridomas were identified that produced 60 to 80% suppression of in vitro polyclonal immunoglobulin production when cocultured with pokeweed mitogen- (PWM) stimulated peripheral blood lymphocytes. Further, one of the suppressor T cell hybridomas constitutively secreted a soluble suppressor factor(s) (TsF) of m.w. 70,000 to 85,000 daltons, which produced reversible noncytotoxic inhibition of lectin-activated B cell Ig production. In contrast, this TsF did not inhibit lectin- or antigen-induced T cell proliferation, nor did it interfere with the generation or effector function of cytotoxic T cells. Additional studies indicated that this Tsf acts directly on B cells or monocytes rather than indirectly modulating the activity of immunoregulatory T cells. In summary, these studies suggest that techniques of somatic cell fusion may provide a valuable approach to further study human immunoregulatory cell-cell interactions as well as provide a source of sufficient quantities of important lymphokines for further purification and characterization.
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PMID:Production of human suppressor T cell hybridomas. 621 85

The three-dimensional structures of LG/LNS domains from neurexin, the laminin alpha 2 chain and sex hormone-binding globulin reveal a close structural relationship to the carbohydrate-binding pentraxins and other lectins. However, these LG/LNS domains appear to have a preferential ligand-interaction site distinct from the carbohydrate-binding sites found in lectins, and this interaction site accommodates not only sugars but also steroids and proteins. In fact, the LG/LNS domain interaction site has features reminiscent of the antigen-combining sites in immunoglobulins. The LG/LNS domain presents an interesting case in which the fold has remained conserved but the functional sites have evolved; consequently, making predictions of structure-function relationships on the basis of the lectin fold alone is difficult.
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PMID:LG/LNS domains: multiple functions -- one business end? 1140 9