Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.2.7 (adenine phosphoribosyltransferase)
 692 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using radiochemical methods, we determined the activities of various enzymes of purine and pyrimidine metabolism in homogenates of human skeletal muscle and of cultured human muscle cells. Results show a large discrepancy between the enzyme activities in muscle and cultured cells. With regard to purine metabolism, adenylate (AMP) deaminase activity was only 1-3% in cultured cells compared to that in muscle, whereas the activity of adenosine deaminase, purine-nucleoside phosphorylase, adenosine kinase, adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase was 7-15-fold higher in the cultured cells. The enzymes of pyrimidine metabolism, orotate phosphoribosyltransferase, orotidine 5'-monophosphate decarboxylase and uridine kinase showed activity of 100-200-fold higher in cultured cells than in adult muscle. The differences in enzyme activity are probably related to the low differentiation stage and the absence of contractile activity in the cultured muscle cells. Care must be taken when using these cells as a model for studying purine and pyrimidine metabolism of adult myofibers.
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PMID:Purine and pyrimidine metabolism in human muscle and cultured muscle cells. 283 95

Cellular brassinolide (BL) levels regulate the development of Brassica napus microspore-derived embryos (MDEs). Synthesis and degradation of nucleotides were measured on developing MDEs treated with BL or brassinazole (BrZ), a biosynthetic inhibitor of BL. Purine metabolism was investigated by following the metabolic fate of (14)C-labelled adenine and adenosine, substrates of the salvage pathway, and inosine, an intermediate of both salvage and degradation pathways. For pyrimidine, orotic acid, uridine and uracil were employed as markers for the de novo (orotic acid), salvage (uridine and uracil), and degradation (uracil) pathways. Our results indicate that utilization of adenine, adenosine, and uridine for nucleotides and nucleic acids increased significantly in BL-treated embryos at day 15 and remained high throughout the culture period. These metabolic changes were ascribed to the activities of the respective salvage enzymes: adenine phosphoribosyltransferase (EC 2.4.2.7), adenosine kinase (EC 2.7.1.20), and uridine kinase (EC 2.7.1.48), which were induced by BL applications. The BL promotion of salvage synthesis was accompanied by a reduction in the activities of the degradation pathways, suggesting the presence of competitive anabolic and catabolic mechanisms utilizing the labelled precursors. In BrZ-treated embryos, with depleted BL levels, the salvage activity of both purine and pyrimidine nucleotides was reduced and this was associated to structural abnormalities and poor embryonic performance. In these embryos, the activities of major salvage enzymes were consistently lower to those measured in their control (untreated) counterparts.
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PMID:Brassinolide-improved development of Brassica napus microspore-derived embryos is associated with increased activities of purine and pyrimidine salvage pathways. 2093 Dec 22