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Fairy rings resulting from a fungus-plant interaction appear worldwide. 2-Azahypoxanthine (AHX) and imidazole-4-carboxamide (ICA) were first isolated from the culture broth of one of the fairy ring-forming fungi, Lepista sordida . Afterward, a common metabolite of AHX in plants, 2-aza-8-oxohypoxanthine (AOH), was found in AHX-treated rice. The biosynthetic pathway of the three compounds that are named as fairy chemicals (FCs) in plants has been partially elucidated; however, that in mushrooms remains unknown. In this study, it was revealed that the carbon skeletons of AHX and ICA were constructed from Gly in L. sordida mycelia and the fungus metabolized 5-aminoimidazole-4-carboxamide (AICA) to both of the compounds. These results indicated that FCs were biosynthesized by a diversion of the purine metabolic pathway in L. sordida mycelia, similar to that in plants. Furthermore, we showed that recombinant adenine phosphoribosyltransferase (APRT) catalyzed reversible interconversion not only between 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranosyl 5'-monophosphate (AICAR) and AICA but also between ICA-ribotide (ICAR) and ICA. Furthermore, the presence of ICAR in L. sordida mycelia was proven for the first time by LC-MS/MS detection, and this study provided the first report that there was a novel metabolic pathway of ICA in which its ribotide was an intermediate in the fungus.

A Spongosorites sp. collected off southern Australia has yielded 1, 9-dimethylhypoxanthine (4). The structure for 4 was solved by spectroscopic analysis.

The important immunosuppressive properties of seminal plasma have significant functions in the processes of reproduction. They mask the presence of an immunostimulating activity. From bovine seminal plasma two active factors have been isolated and characterized with marked enhancing activity for in vitro PHA-dependent lymphocyte transformation. They have inosine and hypoxanthine structures, as confirmed by UV absorption profiles, TLC, mass spectrometry, HPLC patterns, behavior to enzymatic treatments, and breaking of purine ring after acid treatment. Nevertheless, their biological activities are about two orders of magnitude higher than those of commercially available inosine and hypoxanthine standards. Biological activities became practically identical when these were processed (HPLC) in the same way as native molecules. A study to explain such a discrepancy is in progress.

A sensitive and simple micromethod for the accurate measurement of GMP reductase (EC 1.6.6.8) activity in crude extracts is described. The reaction product of [8-14C]IMP was separated from the substrate [8-14C]GMP by descending chromatography on Whatman DE81 ion-exchange paper. This separation method provides an analysis of the possible interfering reactions, such as the metabolic conversion of the substrate GMP to GDP, GTP, and/or guanosine, and guanine and the loss of the product IMP to inosine, hypoxanthine, and other metabolites. Low blank values (70-90 cpm) were obtained consistently with this assay because the IMP spot moves faster than the GMP spot. The major advantages of this method are direct measurement of GMP reductase activity in crude extracts, high sensitivity (with a limit of detection of < 10 pmol of IMP production), high reproducibility (< +/- 5%), and capability to measure activity in small samples (9 micrograms protein).

Bovine follicular fluid (bFF) blocks the occurrence of spontaneous germinal vesicle breakdown (GVBD) of isolated mouse oocytes. One of the active factors was purified by ultrafiltration through a PM-10 membrane filter, gel filtration through Sephadex G-25, and HPLC using a reversed-phase ODS-3 column and a Superose 12 column. This factor was identified as hypoxanthine by gas chromatography and mass spectrometry. The purified substance and hypoxanthine showed the same retention time on HPLC, and identical UV absorbance and mass spectra. There are other oocyte maturation inhibitors in follicular fluid that should be identified.

A selective assay for orthophosphate in complex matrices was developed based on the nucleoside phosphorylase catalyzed conversion of inosine and orthophosphate of hypoxanthine. The enzyme reaction was using only 0.28 units/assay was allowed to proceed for 30 min before quenching. Separation of inosine and hypoxanthine was performed by reversed-phase high-performance liquid chromatography. Quantitation of the hypoxanthine peak was found to be linear with orthophosphate up to 30 micrograms/g. A detection limit of 0.75 ppm could be obtained after dialysis of the commercial enzyme. Interference studies showed that the enzymatic assay unlike the colorimetric molybdate-blue technique was essentially unaffected by complex matrices such as serum, urine, polyphosphates, and phosphoesters.

Isoguanine (2) was found to be an antineoplastic constituent of Prioneris thestylis Dbldy. wings. Three other purine components of the butterfly wings were identified as hypoxanthine (3), uric acid (4) and xanthine (5). Isolation of urocanic acid (6) from the same wing material represented the first detection of this interesting histidine derivative in an arthropod.

Transfer factor was prepared from the leukocyte lysates of four donors with known skin test reactivity. After ultrafiltration and double-gel filtration on polyacrylamide gels, fraction IV of the preparation was found to have biologic activity. This fraction contained one major and occasionally one minor ultraviolet-absorbing and zero to one ninhydrin-detectable spots on thin-layer chromatography. The major ultraviolet spot was identified as hypoxanthine. Hypoxanthine was demonstrated to be responsible for the high 260 nm/280 nm ratio of preparations with biologic activity in vivo. It was not determined if hypoxanthine is required for transfer factor activity. In addition, an orcinol-negative preparation also had biologic activity.

A slow conversion of adenine residues to hypoxanthine occurs in single-stranded DNA when heated in neutral aqueous buffers. The rate of this reaction at pH 7.6 and 110 degrees C is k = 4 x 10(-8) s-1, as determined by base analysis of heat-treated DNA that contains radioactively labeled adenine residues. It is proposed that adenine deamination is one of several forms of hydrolytic damage that may occur as spontaneous premutagenic lesions in DNA in vivo. Cell extracts from calf thymus and human fibroblasts contain a DNA glycosylase activity with specifically catalyzes the release of free hypoxanthine from DNA or polydeoxyribonucleotides that contain dIMP residues. Several properties of the purified enzyme from calf thymus are described: It has an approximate molecular weight of 31 000. No cofactors are required for activity. The enzymatic release of hypoxanthine occurs readily from double-stranded polydeoxyribonucleotides that have either thymine or cytosine residues in the complementary strand. Single-stranded polymers are 10-20-fold more slowly attacked, and there is no detectable cleavage of monomeric dIMP. Hypoxanthine is liberated from DNA directly as a free base. Thus, when poly(dI) x poly(dC) containing both [3H]-dIMP and [32P]dIMP residues was employed as the substrate, 3H-labeled hypoxanthine but no 32P-labeled material was released in ethanol-soluble form. The hypoxanthine-DNA glycosylase presumably acts in DNA repair by preventing deaminated adenine residues from being expressed as mu.

In a search for endogenous regulators for cyclic nucleotide phosphodiesterase (3':5'-cyclic-AMP 5'-nucleotidohydrolase, EC 3.1.4.17), we found that the ultrafiltrate of bovine brain homogenate contained a cyclic nucleotide phosphodiesterase inhibitor. The inhibitor-containing fraction was further purified by ion-exchange column chromatography and gel filtration chromatography. The purified inhibitor was found to be a small molecular weight compound which had a maximum absorption at 248 nm. This compound was identified by thin-layer chromatography and high-pressure liquid chromatography as hypoxanthine. We suggest that hypoxanthine may serve as an endogenous regulator for the hydrolysis of cyclic nucleotide by cyclic nucleotide phosphodiesterase.

Various methods are described for the analysis of purine derivatives in biological samples by ion-pair high-performance liquid chromatography (HPLC) with both gradient and isocratic systems. A new approach is proposed that is suitable for the separation of nuclei acid constituents in different cells with a specific enzymatic activity pattern. The ion-pair HPLC methods were developed for the analysis of erythrocytes, lymphocytes and mitochondria acid-soluble fractions in clinical and experimental studies of normal and altered nucleotide metabolism. The results of studies of purine metabolite redistribution in mouse liver mitochondria during a 30-min incubation at 37 degrees C and data on purine metabolic alterations in mouse thymocytes during hepatoma growth are discussed.

The nature of inhibitors of [3H]-diazepam (D) specific binding (SB) was studied in 2 fractions of acidic extract from bovine brain cortex. Preparative high-performance liquid chromatography (HPLC), mass spectrometry, UV and IR techniques identified hypoxanthine and inosine as inhibitors of SB D. These substances may participate in the neuronal activity control which is in part mediated by the benzodiazepine receptors.

Two cell-division-promoting factors, which have partition coefficients of 1.9 and 2.75 determined by 500-tube countercurrent distribution in a butanolwater system, have been repeatedly isolated in this laboratory from crown gall tumor tissues of Vinca rosea L. These substances have been given the trivial names cytokinesin I and cytokinesin II, respectively. Chemical and mass spectrometric analyses suggest that both cytokinesins are substituted hypoxanthines and are thus very different compounds from the 6-substituted adenyl cytokinins. Carlos Miller, using a very different and far more drastic isolation procedure, obtained one main cell-division-promoting factor from these same tumor tissues, which he identified as ribosyl-trans-zeatin. On the basis of this finding, and without an attempt to repeat our studies, questions have been raised by Miller concerning the existence of the cytokinesins as biologically active substances. We have, therefore, compared some pertinent physical, chemical, and biological properties of the cytokinesins with those of zeatin riboside, have demonstrated that these three substances can be cleanly separated from one another by a number of different methods and that each behaves as a pure substance in the several systems, and, finally, we have shown that the cytokinesins are not contaminated with ribosyl-trans-zeatin and thus do not owe their biological activity to such a contaminant.