162 research outputs found
On the validity of continuous spectrophotometric assays for adenosine deaminase activity: A critical reappraisal
No full textKinetic investigations on adenosine deaminase from calf intestinal mucosa by spectrophotometric monitoring of the reaction at 264, 270, or 228 nm show that this method does not produce artifactual inhibition by substrate excess up to 0.7 mm concentration, when either adenosine or 2â2-deoxyadenosine are employed with calf adenosine deaminase. The evaluation of kinetic parameters for this system was carried out both by initial rate measurements and by numerical differentiation of time progress curves according to a recently published method (S. C. Koerber and A. L. Fink, 1987, Anal. Biochem. 165, 75-87). The following results were obtained by the latter method at pH 7.0 and 30°C: for the conversion of adenosine to inosine, kcat= 251 ± 15 s-1, KMs= 29.7 ± 2.8 Î1⁄4m, KMp= 613 ± 62 Î1⁄4m; for the conversion of 2â2-deoxyadenosine to 2â2-deoxyinosine, kcat= 283 ± 17 s-1, KMs= 22.4 ± 2.2 Î1⁄4m, KMp= 331 ± 35 Î1⁄4m. At 285 nm, a slight negative deviation from Beer's law was observed for adenosine at concentrations higher than 0.9 mm. No deviation was found for inosine up to 2.0 mm at the same wavelenth. © 1991
On the Physiological Role of Cytosolic 5 '-nucleotidase II (cN-II): Pathological and Therapeutical Implications
No full textAmong the members of the 5'-nucleotidase family, there is only one membrane-bound ectosolic isoenzyme. This esterase prefers AMP as substrate but can hydrolyze a number of purine and pyrimidine phosphorylated compounds, indicating that no evolutive pressure to develop a more restricted specificity was exerted on this enzyme. On the contrary, five cytosolic isoforms have been evolved, probably by convergent evolution, showing different and restricted substrate specificity. The different isoforms have different level of expression and distribution in organs of vertebrates. The cytosolic nucleotidase specific for IMP and GMP (cN-II), is an enzyme allosterically regulated, structurally strongly conserved and expressed at a low but constant level in all organs and tissues in vertebrates. As far as we know, alteration of cN-II expression is limited to pathological conditions. In this review, we report the results of the modulation of cN-II specific activity exerted by silencing or hyperexpression in different cell types, in the attempt to better understand its role and implications in pathology and therapy
Enzymatic synthesis of purine 2'-deoxyriboside and its properties as an inhibitor of adenosine deaminases from calf intestinal mucosa and Bacillus cereus
No full textEnzymatic synthesis of purine 2'-deoxyriboside was obtained by reacting purine with excess 2-deoxy-alpha-D-ribose-1-phosphate in the presence of commercial bovine nucleoside phosphorylase; the product was isolated by semipreparative reverse phase HPLC with an overall 62% yield. Purine 2'-deoxyriboside was shown to behave as a competitive inhibitor of adenosine deaminase from calf intestinal mucosa and Bacillus cereus, with apparent Ki values of 4.5 and 8.5 microM, respectively
Interplay between adenylate metabolizing enzymes and AMP-activated protein kinase
No full textPurine nucleotides are involved in a variety of cellular functions, such as energy storage and transfer, and signalling, in addition to being the precursors of nucleic acids and cofactors of many biochemical reactions. They can be generated through two separate pathways, the de novo biosynthesis pathway and the salvage pathway. De novo purine biosynthesis leads to the formation of IMP, from which the adenylate and guanylate pools are generated by two additional steps. The salvage pathways utilize hypoxanthine, guanine and adenine to generate the corresponding mononucleotides. Despite several decades of research on the subject, new and surprising findings on purine metabolism are constantly being reported, and some aspects still need to be elucidated. Recently, purine biosynthesis has been linked to the metabolic pathways regulated by AMP-activated protein kinase (AMPK). AMPK is the master regulator of cellular energy homeostasis, and its activity depends on the AMP : ATP ratio. The cellular energy status and AMPK activation are connected by AMP, an allosteric activator of AMPK. Hence, an indirect strategy to affect AMPK activity would be to target the pathways that generate AMP in the cell. Herein, we report an up-to-date review of the interplay between AMPK and adenylate metabolizing enzymes. Some aspects of inborn errors of purine metabolism are also discussed
Elementi di bilancio e di management. Vol. 2: Strumenti manageriali per il governo economico dell'azienda (Seconda edizione)
No full textIl volume tratta degli strumenti a disposizione del management nel governo economico dell'azienda
Elementi di bilancio e di management. Strumenti manageriali per il governo economico dell'azienda. Volume II
No full textPhotoionization of a Laser Cooled Atom BeamFrontiers in Optics 2012/Laser Science XXVIII
No full textFunctions of the multi-interacting protein KIDINS220/ARMS in cancer and other pathologies
No full textDevelopment of an organ and subsequently the whole system from an embryo is a highly integrated process. Although there is evidence that different systems are interconnected during developmental stages, the molecular understanding of this relationship is either not known or only to a limited extent. Nervous system development, amongst all, is maybe the most crucial and complex process. It relies on the correct distribution of specific neuronal growth factors and hormones to the specific receptors. Among the plethora of proteins that are involved in downstream signalling of neuronal growth factors, we find the kinase-D interacting substrate of 220 kDa (KIDINS220), also known as ankyrin-rich repeat membrane spanning (ARMS) protein. KIDINS220 has been shown to play a substantial role in the nervous system and vascular system development as well as in neuronal survival and differentiation. It serves as a downstream regulator for many important neuronal and vascular growth factors such as vascular endothelial growth factor (VEGF), the neurotrophin family, glutamate receptors and ephrin receptors. Moreover, activation and differentiation of B- and T-cells, as well as tumour cell proliferation has also shown to be related to KIDINS220. This review comprehensively summarises the existing research data on this protein, with a particular interest in its role in cancer and in other pathologies
Elementi di bilancio e di management. Il bilancio di esercizio. Principi, schemi e criteri di valutazione. Volume I
No full textElementi di bilancio e di management. Vol. 1: Il bilancio di esercizio : principi, schemi e criteri di valutazione (Seconda edizione)
No full textIl volume è interamente dedicato al bilancio di esercizio
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