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[Study of inosine transformation into 5'-inosinic acid by the culture of Pseudomonas trifoli].

The transformation of inosine into 5'-inosine acid by Pseudomonas trifolii cells was studied. The synthesis of 5'-inosine acid can be performed by both live intact and dry cells. The effectiveness of inosine phosphorylation depends on the ratio of the inosine and phosphate donor concentrations and the amount of cells. The temperature and pH effect on activity of nucleoside phosphotransferase, phosphomonoesterase and 5'-nucleotidase has been studied. The influence of surface active substances and metal ions on the synthesis of 5'-inosine acid has been investigated. Optimal conditions for the inosine transformation by the above culture have been established.

Cations, Divalent↗
PubMed1977

Factors affecting inosinate synthesis and inosine triphosphate accumulation in human erythrocytes.

Measurements of rates of inosinate synthesis from radioactive hypoxanthine by human erythrocytes show a large degree of individual variation. Rates of inosinate synthesis also vary with the pH and phosphate concentration of the incubation medium. This may be due to changes in the rate of phosphoribosyl pyrophosphate synthesis, and the stimulatory effect of phosphate on this process seems to be more important than the inhibitory effect of 2,3-diphodphoglycerate. The rate of inosinate synthesis, and especially the extent of accumulation of inosine triphosphate, increase disproportionately with time of incubation up to at least 24 h. Storage of erythrocytes also tends to increase inosinate synthesis and inosine triphosphate accumulation.

Anaerobiosis↗
PubMed1976

Germination of unactivated spores of Bacillus cereus T. Effect of preincubation with L-alanine or inosine on the subsequent germination.

Heat-activated spores of Bacillus cereus T germinate rapidly in the presence of L-alanine alone or inosine alone. In contrast, unactivated spores can not germinate in the presence of either germinant alone but rapidly in the presence of both germinants. The highest level of cooperative action of L-alanine and inosine on the germination was observed when they were present in a ratio 1:1. Preincubations of unactivated spores with L-alanine or inosine had opposite effects on the subsequent germination in the presence of both germinants: preincubation with L-alanine stimulated the initiation of subsequent germination, while preincubation with inosine inhibited it. These results suggest that germination of unactivated spores initiated by L-alanine and inosine includes two steps, the first initiated by L-alanine and the second prompted by inosine. The effect of preincubation of unactivated spores with L-alanine was not diminished by washings. The pH dependence of the preincubation of unactivated spores was not so marked as that of the subsequent germination in the presence of inosine.

Alanine↗
PubMed1976

Latency of inosine-5'-diphosphatase in microsomes isolated from rat liver.

The latency of inosine-5'-diphosphatase has been studied in microsomes isolated from rat liver. The appearance of latent activity was the result of an increase in the Vmax of the enzyme. This was observed when assays were carried out in the presence of sodium deoxycholate, after microsomes were treated wtih phospholipase C, or at pH 10.3 and after microsomes were subjected to nitrogen cavitation. The apparent Km of inosine-5'-diphosphatase for IDP was unchanged when microsomes were treated with phospholipase C or at pH 10.3 after both these treatments approximately 85% of the enzyme remained bound to the membrane. In contrast, when microsomes were treated with phospholipase C or at pH 10.3 after both these treatments approximately 85% of the enzyme remained bound to the membrane. In contrast, when microsomes were treated with sodium deoxycholate or subjected to nitrogen cavitation, approximately 75% of the inosine-5'-diphosphatase activity was released from the membrane, and the apparent Km of the enzyme for IDP increased 4- and 2-fold, respectively. Microsomal cisternae were loaded with lead phosphate by incubation with glucose-6-P and Pb2+, and the release of this lead phosphate following the addition of EDTA to the medium was determined to estimate the permeability of the microsomal membrane. When microsomes were treated with sodium deoxycholate, phospholipase C, or at alkaline pH, the microsomal membrane became almost completely permeable to EDTA under conditions where there was little or no increase in the activity of inosine-5'-diphosphatase. Microsomes were treated at pH 10.3 and then adjusted slowly to pH 7.5. The activity of inosine-5'-diphosphatase decreased to the same activity observed in untreated preparations. The results seem of exclude the possibility that latent inosine-5'-diphosphatase activity is the result of an increased permeability of the membrane to IDP. They are, however, consistent with the presence of a noncompetitive inhibitor of the enzyme in the microsomal membrane.

Animals↗
PubMed1976

Enhanced preservation of the ischaemic kidney with inosine.

The function of rat kidneys subjected to 60 minutes of warm ischaemia at body-temperature was notably protected by the prior administration of the purine nucleoside inosine as a 40 mg/ml solution maintained at 37 degrees C. With direct intrarenal arterial perfusion of the kidney at the onset of ischaemia or with intraperitoneal (i.p.) injection 40 minutes before ischaemia, the plasma-creatinine at 24 hours was significantly lower (P less than 0-001) than that of untreated 60-minute-ischaemia controls and not significantly different from that of non-ischaemic unilateral-nephrectomy controls. Intravenous inosine 20 minutes beforehand also afforded significant (P less than 0-01) protection. 7-day survival was 100% in 30 inosine-pretreated rats and 65% in 45 rats with all other types of pre-treatment (P less than 0-001). Although i.p. adenosine was better (P less than 0-05) than no treatment, i.p. inosine was better (P less than 0-02) than i.p. adenosine. Allopurinol, phenoxybenzamine, A.T.P., or cyclic A.M.P. caused no improvement over controls. Kidneys perfused with inosine maintained higher purine-nucleotide levels during ischaemia and rapidly resynthesised A.T.P. when blood-flow was restored in vivo.

Adenosine↗
PubMed1976

Hemoglobin function in stored blood, XVII. Maintenance of red cell 2,3 DPG (function) and ATP (viability) for six weeks in ACD or CPD-adenine-inosine-methylene blue.

Blood preservatives containing adenine for six week storage have been prepared with inosine and methylene blue at various pH levels in order to maintain, 23-DPG levels for immediate oxygen transport upon transfusion. In one experiment, the adverse effect of a high pH on ATP maintenance was demonstrated in the presence of methylene blue and inosine. In this and other experiments it was clear that ATP was better maintained in low pH preservatives and DPG better maintained in higher pH preservatives. However, 2,3-DPG levels were kept from falling with CPD-adenine-inosine over a wide range of pH values. A CPD-adenine-inosine preservative at a pH 5.8 maintained normal DPG levels for three weeks of storage. A similar preservative but with a pH of 6.6 maintained normal DPG levels for 35 days of storage. It is suggested that if all blood bank units are going to have normal DPG levels for optimal oxygen transport at the time of transfusion then a CPD preservative with a higher pH and/or metabolic nutrients and regulators such as inosine or methylene blue would be required.

Adenine↗
PubMed1977

Mutation of an inosine-producing strain of Bacillus subtilis to DL-methionine sulfoxide resistance for guanosine production.

An inosine-producing strain of Bacillus subtilis was mutated to resistance against the antagonist of glutamine, DL-methionine sulfoxide. Among the mutants derived, guanosine producers were observed frequently. The best strain, 14119, produced 9.6 g of guanosine per liter at a weight yield of 12% from consumed sugar. Inosine production decreased concomitantly. When resistance was increased further by exposure to higher doses of DL-methionine sulfoxide, another strain, AG169, was obtained that did not excrete inosine but produced increased amounts of xanthosine. In these strains, the specific activity of 5'-nucleotidase was lower and that of inosine 5'-monophosphate (IMP) dehydrogenase was higher than the parent strain. It is speculated that the metabolic flow from IMP to xanthosine 5'-monophosphate proceeds more smoothly than that from IMP to inosine and yields more xanthosine and guanosine.

Bacillus subtilis↗
PubMed1978

Inosine nucleosidase from Azotobacter vinelandii. Purification and properties.

An enzyme catalyzing the hydrolysis of purine nucleosides was found to occur in the extract of Azotobacter vinelandii, strain O, and was highly purified by ammonium sulfate fractionation, DEAE-cellulose chromatography, hydroxylapatite chromatography and gel filtration on Sephadex G-150. A strict substrate specificity of the purified enzyme was shown with respect to the base components. The enzyme specifically attacked the nucleosides without amino groups in the purine moiety: inosine gave the maximum rate of hydrolysis and xanthosine was hydrolyzed to a lesser extent. The pH optimum of inosine hydrolysis was observed from pH 7 to 9, while xanthosine was hydrolyzed maximally at pH 7. The Km values of the enzyme for inosine were 0.65 and 0.85 mM at pH 7.1 and 9.0, respectively, and the value for xanthosine was 1.2 mM at pH 7.1. Several nucleotides inhibited the enzyme: the phosphate portions of the nucleotides were suggested to be responsible for the inhibition by nucleotides. Although the inhibition of the enzyme by nucleotides was apparently non-competitive type with respect to inosine, allosteric (cooperative) binding of the substrate was suggested in the presence of the inhibitor. The physiological significance of the enzyme was discussed in connection with the degradation and salvage pathways of purine nucleotides.

Azotobacter↗
PubMed1976

Adenosine phosphyorylase activity as distinct from inosine-guanosine phosphorylase activity in Sarcoma 180 cells and rat liver.

Adenosine phosphorylase (EC 2.4.2.-) activity present in Sarcoma 180 cells grown in culture and in rat liver, is shown to be distinct from inosine-guanosine phosphorylase by several criteria: (a) treatment of Sarcoma 180 cell extract with p-chloromercuribenzoate inhibited the two activities to a different extent, (b) adenine selectively protected the adenosine phosphorylase activity of Sarcoma 180 and rat liver extract against heat inactivation, while hypoxanthine selectively protected inosine-guanosine phosphorylase activity, (c) at nearly saturating substrate concentrations and using Sarcoma 180 extract, the rates of ribosylation of a mixture of adenine + hypoxanthine or adenine + guanine, but not of hypoxanthine + guanine, were found to be almost equal to the sum of their individual rates as measured separately, (d) inosine selectively inhibited the ribosylation of hypoxanthine and guanine catalysed by Sarcoma 180 and rat liver extract while 2-chloroadenosine selectively inhibited the ribosylation of adenine and N6-furfuryladenine, (e) pH vs. activity curves were similar with hypoxanthine or guanine as the substrate but they were markedly different from the curve with adenine as the substrate. The potential role of adenosine phosphorylase activity in vivo is discussed.

Adenine↗
PubMed1979

Inosine may be an endogenous ligand for benzodiazepine receptors on cultured spinal neurons.

Mouse spinal neurons grown in tissue culture were used to study the membrane effects of the benzodiazepine flurazepam and the naturally occurring purine nucleoside inosine, which competes for benzodiazepine receptor sites in the central nervous system. Application of inosine elicited two types of transmitter-like membrane effects: a rapidly desensitizing excitatory response and a nondesensitizing inhibitory response. Flurazepam produced a similar excitatory response which showed cross-desensitization with the purine excitation. Flurazepam also blocked the inhibitory inosine response. The results provide electrophysiological evidence that an endogenous purine can activate two different conductances on spinal neurons and that flurazepam can activate one of the conductances and antagonize the other.

Animals↗
PubMed1977

The heart production in energy-depleted human erythrocytes induced by glucose, inosine and adenine.

The heat production (HP) of glucose deprived human red blood cells was measured, using glucose, adenine and inosine as substrates. Inosine induced a significantly higher HP than glucose and adenine induced no significant HP. At low pH the HP of glucose decreased more than that of inosine, corresponding to an equally lowered lactate production. The results indicate that it should be possible to use the system developed to study the functional state both of the complete glycolytic system and the lower part of it in intact red blood cells during various clinical conditions.

Adenine↗
PubMed1978

Guanosine triphosphate catabolism in human and rabbit erythrocytes: role of reductive deamination of guanylate to inosinate.

The reductive deamination of guanylate to inosinate was demonstrable but occurred at low rates in human and rabbit erythrocytes incubated in vitro with or without glucose. However, the process was considerably accelerated in erythrocytes incubated with deoxyglucose. In human erythrocytes incubated with deoxyglucose, deamination was the major pathway of catabolism of guanylate; little or no guanylate was dephosphorylated. In rabbit erythrocytes, guanylate was both deaminated and dephosphorylated. Inosinate formed from guanylate was metabolized only by dephosphorylation in human erythrocytes, but in rabbit erythrocytes, it was also converted to xanthylate.

Animals↗
PubMed1979

Purification and properties of human erythrocyte inosine triphosphate pyrophosphohydrolase.

Inosine triphosphate pyrophosphohydrolase from human erythrocytes was purified and characterized. The enzyme is highly specific for ITP and shows optimal activity in glycine buffer pH 9.6 and 50 mM MgCl2. The Km of the enzyme is 1.3 X 10(-4), the Vmax = 1.2 X 10(-9) and the Keq = 3.8 X 10(4). Human erythrocyte ITP pyrophosphohydrolase does not require SH compounds for activation. The enzyme is inhibited by Cd++, Co++, and Ca++ ions and by p-hydroxymercuribenzoate.

Cations, Divalent↗
PubMed1978

In vitro effects of inosine-pyruvate-phosphate on P50 values and DPG contents of fresh and stored blood from healthy neonates, symptom-free premature infants and premature infants with respiratory distress syndrome.

A study was made of the effect of a 3-hour incubation with inosine-pyruvate-phosphate (IPP) on the P50 values and 2,3-DPG contents of fresh blood and blood which had stood for 96 h, from healthy adults, term neonates, 1-2-week-old symptom-free premature infants and RDS premature infants. It was found that the P50 value and the 2,3-DPG content could be increased considerably by IPP treatment in both the fresh and the stood blood in the various groups of neonates. The question remains open as to whether the effect of IPP, in significantly improving the O2 transport in neonates, is a consequence of the 2,3-DPG alone or of some other metabolite. In RDS the stimulating effect of the IPP mixture is appreciably lower.

Adult↗
PubMed1977

Temperature induced transition of the pH-activity curve of heavy meromyosin adenosine triphosphatase and inosine triphosphatase.

The pH-activity curve of heavy meromyosin ATPase [EC 3.6.1.3] was measured at various temperatures. The pH-activity curve at higher temperatures showed a maximum at low pH and a minimum at pH 7 to 8 as has been already reported. At lower temperatures it was sigmoidal in shape, similar to a simple dissociation curve of pKa 6 to 7. The pH-activity curve at intermediate temperatures appeared to be inbetween the two extreme shapes. These changes in pH-activity curve with temperature were found to be common in the presence of divalent cations such as Mg2+, Mn2+, and Ca2+. The ATPase mechanism may be identical in the presence of any divalent cation, and the rate determining step revealing the steady state rate alters by changing the temperature. The transition temperatures estimated at pH 8 were 10 degrees, 8 degrees, and about 5 degrees in the presence of MnCl2, CaCl2, and MgCl2, respectively. The difference in the temperature coefficients above and below the transition temperature was most distinct in the presence of MnCl2, and vague in the presence of CaCl2. A similar change of pH-activity curve with temperature was found with heavy meromyosin ITPase in the presence of MgCl2.

Adenosine Triphosphatases↗
PubMed1976

Studies on inosine monophosphate dehydrogenase. Isotope exchange at equilibrium.

Investigations on the mechanism of the IMP dehydrogenase (IMP: NAD+ oxidoreductase, EC 1.2.1.14) reactions have been made at pH 7.0 by measuring rates of isotope exchange at chemical equilibrium with K+ maintained at a constant concentration. The results are generally in accord with the conclusions reached on the basis of the steady-state kinetic data obtained previously and confirm that there is random addition of IMP and NAD to the enzyme. The data also indicate clearly that at pH 7.0 catalysis is faster than the rate of IMP and/or XMP release which is rate limiting for the reaction sequence. The binding of IMP to the enzyme at pH 8.1 has been demonstrated to occur in the absence of both K+ and NAD and id independent of the K+ concentration.

Carbon Radioisotopes↗