Adenosine isolation

To determine the fate of the 2 - and 3 -hydrogen atoms of adenosine in the conversion of adenosine into arabinosyladenine, experiments with [2 -3H, U-l4C]adenosine and D-[3-3H, U-14C]ribose were performed. Arabinosyladenine derived from [2 -3H, U-,4C]adenosine had lost all of its tritium, whereas adenosine isolated from the RNA of the organism had about the same 3H 14C ratio as the added adenosine. In the D-[3-3H, U-14C]ribose experiment, the proportion of tritium in arabinosyladenine was only 33% of that present in the adenosine from RNA. 

Riboflavin-5 -Adenosine Diphosphate. Riboflavin-5 -adenosine diphosphate [146-14-5] (flavin—adenine dinucleotide, FAD), C27H33N9O15P2 (2), mol wt 785.56, was first isolated in 1938 from the D-amino acid oxidase as its prosthetic group (95), where it was postulated to be... 

Amino-2 -deoxypurines. 2 -AmiQo-2 -deoxyadenosine (15) is a naturally occurring A[-nucleoside isolated from A.ctinomadura that shows antknycoplasmal activity (1,4). Adenosine is the direct precursor for its biosynthesis (30). 2 -Arnino-2 -deoxyguanosine (16), isolated from a strain of Enterobacter cloacae (1,4), shows the growth of HeLa S3 cells and Sarcoma 180 in vivo and has been tested for antibacterial activity. 

Aristeromycin. Aristeromycin (36), the first carbocyhc analogue of adenosine, was isolated from the culture filtrates of S. citricolor as part of a search for inhibitors of bacterial leaf blight (1—4). A herbicidaHy active hypoxanthine analogue of (36), coaristeromycin, has also been isolated (108). Several chemical syntheses of (36) have appeared (1—4,109). It inhibits Aanthomonas OTjc e and Eyricularia bacterial leaf blight, blast disease of rice plants, and... 

DiaZepin Nucleosides. Four naturally occurring dia2epin nucleosides, coformycin (58), 2 -deoxycoformycin (59), adechlorin or 2 -chloro-2 -deoxycoformycin (60), and adecypenol (61), have been isolated (1—4,174,175). The biosynthesis of (59) and (60) have been reported to proceed from adenosine and C-1 of D-ribose (30,176,177). They are strong inhibitors of adenosine deaminase and AMP deaminase (178). Compound (58) protects adenosine and formycin (12) from deamination by adenosine deaminase. Advanced hairy cell leukemia has shown rapid response to (59) with or without a-or P-interferon treatment (179—187). In addition, (59) affects interleukin-2 production, receptor expression on human T-ceUs, DNA repair synthesis, immunosuppression, natural killer cell activity, and cytokine production (188—194). 

The consequence of ADA deficiency is accumulation of adenosine and 2 -deoxyadenosine, substances toxic to lymphocytes, important cells in the immune response. 2 -Deoxyadenosine is particularly toxic because its presence leads to accumulation of its nucleotide form, dATP, an essential substrate in DNA synthesis. Elevated levels of dATP actually block DNA replication and cell division by inhibiting synthesis of the other deoxynncleoside 5 -triphosphates (see Chapter 27). Accumulation of dATP also leads to selective depletion of cellular ATP, robbing cells of energy. Children with ADA SCID fail to develop normal immune responses and are susceptible to fatal infections, unless kept in protective isolation. 

FIGURE 9.14 Effects of adenosine receptor agonist 2-chloro-adenosine on vascular perfusion pressure of isolated perfused rat kidneys. Minor effects seen in untreated kidneys (filled circles) and pronounced vasoconstriction while vasodilatation in kidneys coperfused with subthreshold concentrations of a-adrenoceptor vasoconstrictor methoxamine and vasodilatatory activation of adenylyl cyclase with forskolin (open circles). Redrawn from [49]. 

Jervis used porous silica coated with chemisorbed polyacrylhydrazide for immobilization of adenosine monophosphate (AMP) [117]. After periodate oxidation of its ribose residue the ligand was coupled to the carrier and used for isolation of lactate dehydrogenase from rabbit muscle. The specific capacity was 2 mg of protein/g adsorbent with a ligand content of 10 pmol/g, whereas recovery of enzymatic activity after elution was 85%. Hipwell et al. [118] found that for effective binding of lactate dehydrogenases on AMP-o-aminoalkyl-Sepharose the spacer arm length required at least 4 methylene links. Apparently, a macromolecule of polyacrylhydrazide acts itself like an extended spacer arm and thus allow AMP to bind the enzyme. 

Pentostatin (deoxycoformycin Fig. 4) is a purine isolated from cultures of Streptomyces antibioticus. Its mode of action involves inhibition of adenosine deaminase, which plays a key role in purine salvage pathways and DNA synthesis. As a consequence, deoxyadenosine triphosphate (dATP) is accumulated, which is highly toxic to lymphocytes. This is associated with augmented susceptibility to apoptosis, particularly in T cells. 

To correlate embryonic arrests with the metabolic pathways, and especially to understand why cellular organelles first undergo chemical damages, biological investigations include evaluation of DNA, RNA, protein, glucose, lipid, and adenosine-5 -triphosphate (ATP) contents, whose fractions are extracted and isolated by modified Schneider methods. In particular,... 

BS Spinowitz, JA Zadunaisky. (1979). Action of adenosine on chloride active transport of isolated frog cornea. Am J Physiol 237 F121-F127. 

In the processes that require regeneration of cofactors such as nicotinamide adenine dinucleotide phosphate (NAD(P)H) and adenosine triphosphate (ATP), whole-cell biotransformations are more advantageous than enzymatic systems [12,15]. Whole cells also have a competitive edge over the isolated enzymes in complex conversions involving multiple enzymatic reactions [14]. 

An isolated DNA molecule comprising DNA which encodes a group III alcohol dehydrogenase and DNA which encodes a BDS-active biocatalyst via nicotinamide adenosine dinucleotide-dependent manner. 

FIGURE 6.3 Quantification on the first half of an isolated peak. The spectrum is from the [2Fe-2S] cluster in the enzyme adenosine phosphosulfate reductase from Desulfovibrio vulgaris (Verhagen et al. 1993). The inset shows the asymmetrical low-field -feature the vertical line at the peak position indicates the rightmost integration limit for quantification on half... 

A triokinase, isolated from liver, phosphorylates both D-glycerose and DL-glycerose, at the same rate, in the presence of adenosine-5-triphosphoric acid (ATP), and phosphorylates dihydroxyacetone at approximately half the rate.77-78... 

Hager and Szostak used an RNA library in which each member was capped by an adenosine-5 -5 -pyrophosphate group at the 5 -end to isolate ribozymes that catalyze the ligation of an oligoribonucleotide to this activated group. This reaction results in the formation of a 3 -5 -ligation and the release of AMP [82]. 

---