Purine spectra, analysis

Upon purification of the XDH from C. purinolyticum, a separate Se-labeled peak appeared eluting from a DEAE sepharose column. This second peak also appeared to contain a flavin based on UV-visible spectrum. This peak did not use xanthine as a substrate for the reduction of artificial electron acceptors (2,6 dichlor-oindophenol, DCIP), and based on this altered specificity this fraction was further studied. Subsequent purification and analysis showed the enzyme complex consisted of four subunits, and contained molybdenum, iron selenium, and FAD. The most unique property of this enzyme lies in its substrate specificity. Purine, hypoxanthine (6-OH purine), and 2-OH purine were all found to serve as reductants in the presence of DCIP, yet xanthine was not a substrate at any concentration tested. The enzyme was named purine hydroxylase to differentiate it from similar enzymes that use xanthine as a substrate. To date, this is the only enzyme in the molybdenum hydroxylase family (including aldehyde oxidoreductases) that does not hydroxylate the 8-position of the purine ring. This unique substrate specificity, coupled with the studies of Andreesen on purine fermentation pathways, suggests that xanthine is the key intermediate that is broken down in a selenium-dependent purine fermentation pathway. ... 

Inosine 5-phosphate (XXX) was converted to adenylosuccinate [6-(succinylamino)-9-(5-0-phospho-/8-D-ribofuranosyl)purine, XXXI] which was isolated by ion-exchange chromatography and was identified by analysis and by its characteristic absorption spectrum. The stoichiometry of the reaction was also verified by isolation and determination of the reactants. Hydroxylamine could replace L-aspartate, and the product formed was isolated and tentatively identified as iV -hydroxyadenosine 5-phosphate. A crude extract of Escherichia coli B was shown to split adenylosuccinate to adenosine 5-phosphate and fumaric acid. 

Analysis of the data on the chemistry of isomeric thienopyrimidines published over the last 10-15 years shows that this class of heteroaromatic compounds, which are structural analogs of natural compounds of the purine class, attracts increasing interest of chemists and biochemists. In the first half of the 21st century, new approaches to the synthesis of derivatives of these fused heterocyclic systems will be, undoubtedly, extensively developed. These derivatives are not only of theoretical interest but also possess a broad spectrum of practical use, primarily, due to various biological activities. Of the approaches to their synthesis, multicomponent cascade heterocyclization, which allows one to construct various functionalized thienopyrimidines and their fused analogs in one technologically and ecologically safe step, holds the most promise. 

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