Preparation of adenosine nucleotide derivatives suitable for affinity chromatography.
ABSTRACT: Methods of synthesizing a series of chemically-defined AMP, ADP, ATP, adenylyl imidodiphosphate and pyrophosphate derivatives suitable for affinity chromatography are extensively described. Each derivative has a single primary amino group at the end of a hexamethylene ;spacer' chain for attachment to CNBr-activated agarose. The synthesis of the derivative where the ;spacer' arm is attached directly to the 8 position of the adenine ring to produce 8-(6-aminohexyl)amino-AMP involves the direct bromination of AMP in the 8 position followed by displacement of the halogen by 1,6-diaminohexane. This monophosphate derivative can then be converted into the corresponding di- or triphosphate forms by direct phosphate condensation with carbonyl di-imidazole. A second series of adenosine phosphate derivatives with the phosphate moieties unsubstituted has been similarly prepared from N(6)-(6-aminohexyl)-AMP (Guilford et al., 1972). A third type of ligand has been synthesized by condensing the phosphoryl imidazolide of AMP with 6-aminohex-1-yl phosphate. This compound, P(1)-(6-aminohex-1-yl) P(2)-(5'-adenosyl) pyrophosphate, has an unsubstituted adenine ring. The synthesis of a fourth type of ligand, 6-aminohex-1-yl pyrophosphate, was done by heating 6-aminohexan-1-ol with crystalline pyrophosphoric acid under reduced pressure. The structures of the synthesized compounds were confirmed by chemical, electrophoretic and chromatographic methods and by u.v. spectrometry. The general applicability of the synthetic methods used is discussed in relation to the preparation of other affinity adsorbents. Examples are given where these derivatives have been successful in reversibly binding dehydrogenases, kinases and myosin and its proteolytic subfragments. The partial purification of rat liver glucokinase on an ADP derivative is shown.
Project description:1. It has been reported that the rate of purine nucleotide synthesis de novo in the immature rat uterus is doubled at 6h after administration of oestradiol-17beta. The present work confirms an increased incorporation of glycine and adenine into uterine nucleotides between 2 and 6h after hormone treatment and investigates the mechanism of this response. 2. Activation of regulatory enzymes is unlikely to promote increased nucleotide synthesis: the activities of 5-phosphoribosyl 1-pyrophosphate amidotransferase (EC 220.127.116.11) and adenine phosphoribosyltransferase (EC 18.104.22.168) are the same in uterine extracts from control and oestrogen-treated rats. 3. Therefore it was proposed that oestradiol might promote an increased supply of a rate-limiting substrate. The low oestrogen-sensitive rate of AMP synthesis from adenine and endogenous 5-phosphoribosyl 1-pyrophosphate in the intact uterus compared with the high, oestrogen-insensitive rate in uterine extracts supplemented with 5-phosphoribosyl 1-pyrophosphate is evidence that the supply of 5-phosphoribosyl 1-pyrophosphate limits purine nucleotide formation and may increase after hormone treatment. This proposal is supported by the decrease in AMP synthesis in the whole tissue in the presence of guanine and 7-amino-3-(beta-d-ribofuranosyl)pyrazolo[3,4-d]pyrimidine (formycin). These compounds do not inhibit adenine uptake or adenine phosphoribosyltransferase activity, but they both decrease the availability of 5-phosphoribosyl 1-pyrophosphate, the former by promoting its utilization by hypoxanthine/guanine phosphoribosyltransferase (EC 22.214.171.124) and the latter by inhibiting its synthesis from ribose 5-phosphate and ATP by ribose 5-phosphate pyrophosphokinase (EC 126.96.36.199). 4. It is unlikely that the increased availability of 5-phosphoribosyl 1-pyrophosphate results from hormonal stimulation of ribose 5-phosphate formation. Methylene Blue and phenazine methosulphate both increase ribose 5-phosphate without altering the supply of 5-phosphoribosyl 1-pyrophosphate. 5. The activity of ribose 5-phosphate pyrophosphokinase is low in uterine extracts and increases rapidly in response to oestradiol. Therefore the hormonal activation of the routes of purine nucleotide synthesis both de novo and from preformed precursors may be due, at least in part, to an increased availability of the common rate-limiting substrate 5-phosphoribosyl 1-pyrophosphate, mediated by activation of ribose 5-phosphate pyrophosphokinase.
Project description:1. Two adenine nucleotides, 8-(6-aminohexyl)aminoadenosine 3':5'-cyclic monophosphate and 8-(6-aminohexyl)amino-AMP, were synthesized. Their structures were established in particular by using mass spectroscopy. 2. Free cyclic AMP and 8-(6-aminohexyl)amino cyclic AMP both stimulate protamine kinase activity at low concentrations, but are inhibitory at concentrations above 0.1mm. AMP is an inhibitor of enzymic activity, whereas neither 8-(6-aminohexyl)amino-AMP nor the earlier synthesized N(6)-(6-aminohexyl)-AMP is inhibitory. 3. The nucleotides were coupled to Sepharose 4B and used for biospecific chromatography of partially purified protamine kinase. Enzyme applied at high buffer concentrations to the cyclic AMP-Sepharose material was retarded and thereby purified tenfold. At low buffer concentrations the enzyme was adsorbed to the affinity material, and was subsequently released by a pulse of the inhibitor AMP, yielding a 50-100-fold purification. Enzyme applied to immobilized 8-(6-aminohexyl)amino-AMP or N(6)-(6-aminohexyl)-AMP was eluted together with the main protein peak in the void volume. 4. Protamine kinase eluted from 8-(6-aminohexyl)amino cyclic AMP-Sepharose was no longer activated by cyclic AMP. Results from sucrose gradient centrifugation suggest that a dissociation of the enzyme took place on the immobilized nucleotide. 5. Further information on the mass spectroscopy has been deposited as Supplementary Publication SUP 50026 at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1973) 131, 5.
Project description:Ribonuclease A is the archetype of a functionally diverse superfamily of vertebrate-specific ribonucleases. Inhibitors of its action have potential use in the elucidation of the in vivo roles of these enzymes and in the treatment of pathologies associated therewith. Derivatives of adenosine 5'-pyrophosphate are the most potent nucleotide-based inhibitors known. Here, we use X-ray crystallography to visualize the binding of four naturally-occurring derivatives that contain 5'-pyrophosphate-linked extensions. 5'-ATP binds with the adenine occupying the B(2) subsite in the manner of an RNA substrate but with the gamma-phosphate at the P(1) subsite. Diadenosine triphosphate (Ap(3)A) binds with the adenine in syn conformation, the beta-phosphate as the principal P(1) subsite ligand and without order beyond the gamma-phosphate. NADPH and NADP(+) bind with the adenine stacked against an alternative rotamer of His119, the 2'-phosphate at the P(1) subsite, and without order beyond the 5'-alpha-phosphate. We also present the structure of the complex formed with pyrophosphate ion. The structural data enable existing kinetic data on the binding of these compounds to a variety of ribonucleases to be rationalized and suggest that as the complexity of the 5'-linked extension increases, the need to avoid unfavorable contacts places limitations on the number of possible binding modes.
Project description:Phosphatidylinositol 4-phosphate (PtdIns(4)P) lipid is an essential component of eukaryotic membranes and a marker of the Golgi complex. Here, we developed metabolically stabilized (ms) analogs of PtdIns(4)P and the inositol 1,4-bisphosphate (IP(2)) head group derivative and demonstrated that these compounds can substitute the natural lipid fully retaining its physiological activities. The methylenephosphonate (MP) and phosphorothioate (PT) analogs of PtdIns(4)P and the aminohexyl (AH)-IP(2) probe are recognized by the PtdIns(4)P-specific PH domain of four phosphate adaptor protein 1 (FAPP1). Binding of FAPP1 to the PtdIns(4)P derivatives stimulates insertion of the PH domain into the lipid layers and induces tubulation of membranes. Both ms analogs and IP(2) probes could be invaluable for identifying protein effectors and characterizing PtdIns(4)P-dependent signaling cascades within the trans-Golgi network (TGN).
Project description:1. Isolated chick lymphoid cells, together with isolated chick liver and kidney cells, incorporate [1-14C]glycine or [14C]formate into urate. 2. Of the cell types used, bursal cells incorporate 14C into urate at the fastest rate, although the output of total urate by bursal cells is only 10% that of liver cells. 3. When suspended in Eagle's medium the incorporation of 14C into urate is inhibited by adenine and guanine up to 1 mM. In contrast, the addition of 1 mM-AMP or -GMP results in a relatively large stimulation of this incorporation. 4. Added adenine is rapidly taken up by liver cells and then released in an unmetabolized form; AMP is taken up more slowly and is rapidly metabolized. The metabolites (possibly including adenine) are then released. 5. Intracellular liver 5-phosphoribosyl 1-pyrophosphate is approx. 0.7mM and remains constant or falls slightly during a 3 h incubation of the cells. 6. The addition of adenine or guanine, AMP or GMP, does not alter liver intracellular 5-phosphoribosyl 1-pyrophosphate concentrations. Added 5-phosphoribosyl 1-pyrophosphate is not taken up by liver cells. 7. The results are discussed in the context of the control of urate and purine synthesis de novo in the chick.
Project description:It is now well established that the peroxisomal membrane is not freely permeable to small molecules in vivo, which implies the existence of metabolite transporters in the peroxisomal membrane. A few putative peroxisomal metabolite transporters have indeed been identified, but the function of these proteins has remained largely unresolved so far. The only peroxisomal transporter characterized to a significant extent is the adenine nucleotide transporter, which is presumably required to sustain the activity of the intraperoxisomal very-long-chain-acyl-CoA synthetase. In addition to AMP, this acyl-CoA synthetase also produces pyrophosphate, which must be exported from the peroxisome. In the present study, we demonstrate that the peroxisomal membrane contains a transporter activity that facilitates the passage of phosphate and possibly pyrophosphate across the peroxisomal membrane. By reconstitution of peroxisomal membrane proteins in proteoliposomes, some kinetic parameters of the transporter could be established in vitro. The transporter can be distinguished from the mitochondrial phosphate transporter by its different sensitivity to inhibitors.
Project description:The synthesis of an affinity adsorbent, 8-(6-aminohexyl)aminoadenosine 2'-phosphate-Sepharose 4B, is described. The assembly of the 2'-AMP ligand and the hexanediamide spacer arm was synthesized in free solution before its attachment to the Sepharose matrix. This adsorbent retarded the hexameric NADP-specific glutamate dehydrogenase of Neurospora crassa, showing a capacity for this enzyme similar to that of comparable coenzyme-analogue adsorbents for other dehydrogenases. The enzyme was eluted either at pH 6.8 in a concentration gradient of NADP+, or at pH 8.5 in the presence of NADP+ in concentration gradients of either dicarboxylates or NaCl. Anomalous effects of dicarboxylates in facilitating elution are discussed. 2'-AMP and its derivatives, 8-bromoadenosine 2'-phosphate and 8-(l-aminohexyl)aminoadenosine 2'-phosphate, which were used in the synthesis of the adsorbent, all acted as enzyme inhibitors competitive with NADP+. The chromatographic properties of the wild-type enzyme were compared with those of mutationally modified variants containing defined amino acid substitutions. This approach was used to assess the biospecificity of adsorption and elution and the contribution of non-specific binding. The adsorbent showed a low capacity for the enzyme from mutant am1 (Ser-336 replaced by Phe), a variant that has a localized defect in NADP binding, but an otherwise almost normal conformation, suggesting that non-specific interactions are at most weak. The enzyme from mutant am3, a variant modified in a conformational equilibrium, was fully retarded by the adsorbent, but showed a significantly earlier elution position than the wild-type enzyme. This is consistent with measurements in free solution that showed the am3 enzyme to have a higher Ki for 2'-AMP than the wild-type enzyme. The enzyme from mutant am19 was eluted as two distinct peaks at both pH 6.8 and 8.5. The adsorbent was used to separate hybrid hexamers constructed in vitro by a freeze-thaw procedure from pairs of purified variants. Several chromatographically distinct peaks of differing enzymological properties were purified from each hybridization mixture in quantities of up to a few milligrams, and represented distinct species of hybrid hexamers differing in subunit ratio.
Project description:1. The progress curves of adenine phosphoribosyltransferase and of hypoxanthine phosphoribosyltransferase activity plotted against 5-phosphoribosyl pyrophosphate concentration were hyperbolic in nature. The inhibition of the former enzyme by AMP and GMP and of the latter enzyme by IMP and GMP showed completely competitive characteristics. 2. The effect of temperature on the reaction of adenine phosphoribosyltransferase and of hypoxanthine phosphoribosyltransferase was examined. The energy of activation of the former enzyme decreased at temperatures greater than 27 degrees and that of the latter enzyme at temperatures greater than 23 degrees . For each enzyme, the change in the heat of formation of the 5-phosphoribosyl pyrophosphate-enzyme complex at the critical temperature was approximately equal to the change in the energy of activation but was in the opposite direction. The inhibitor constants with both enzymes in the presence of nucleotides varied in different ways with temperature from the Michaelis constants for 5-phosphoribosyl pyrophosphate indicating that different functional groups were involved in binding substrates and inhibitors. 3. ATP was found to stimulate adenine-phosphoribosyltransferase activity at concentrations less than about 250mum and to inhibit the enzyme at concentrations greater than 250mum. The stimulation was unaffected by 5-phosphoribosyl pyrophosphate concentration but the inhibitory effect could be overcome by increasing concentrations of this compound. At low concentrations ATP reversed the inhibition of adenine phosphoribosyltransferase by AMP and GMP to an extent dependent on their concentration. 4. The properties of adenine phosphoribosyltransferase changed markedly on purification. Crude extracts of ascites-tumour cells had Michaelis constants for 5-phosphoribosyl pyrophosphate and adenine 75 and six times as high respectively as those obtained with purified enzyme. ATP had no stimulatory effect on activity of the purified enzyme or on that of crude extracts heated 15min. or longer at 55 degrees . 5. It is suggested that at low concentrations ATP is bound to an ;activator' site which is separate from the substrate binding site of adenine phosphorytransferase and that at high concentrations ATP competes with 5-phosphoribosyl pyrophosphate at the active site of the enzyme.
Project description:1. 5-Phosphoribosyl 1-methylenediphosphonate was isolated after reaction of ribose 5-phosphate and O-adenylyl methylenediphosphonate with 5-phosphoribosyl pyrophosphate synthetase from Ehrlich ascites-tumour cells. 2. The analogue reacted with adenine phosphoribosyltransferase, hypoxanthine phosphoribosyltransferase and nicotinamide phosphoribosyltransferase [K(m) (analogue)/K(m) (5-phosphoribosyl pyrophosphate) 0.17, 0.19 and 6.3 respectively; V(max.) (analogue)/V(max.) (5-phosphoribosyl pyrophosphate) 0.011, 0.26 and 1.1 respectively]. 3. The analogue was not a substrate for 5-phosphoribosyl pyrophosphate amidotransferase or orotate phosphoribosyltransferase. 4. Ribose 5-phosphorothioate was synthesized by allowing ribose to react with thiophosphoryl chloride in triethyl phosphate. The analogue was a substrate for 5-phosphoribosyl pyrophosphate synthetase from Ehrlich ascites-tumour cells. When this reaction was coupled to either adenine phosphoribosyltransferase or hypoxanthine phosphoribosyltransferase, adenosine 5'-phosphorothioate or inosine 5'-phosphorothioate was formed respectively.
Project description:1. Phenylalanyl-tRNA synthetases have been partially purified from cotyledons of seeds of Aesculus californica, which contains 2-amino-4-methylhex-4-enoic acid, and from four other species of Aesculus that do not contain this amino acid. The A. californica preparation was free from other aminoacyl-tRNA synthetases, and the contaminating synthetase activity in preparations from A. hippocastanum was decreased to acceptable limits by conducting assays of pyrophosphate exchange activity in 0.5m-potassium chloride. 2. The phenylalanyl-tRNA synthetase from each species activated 2-amino-4-methylhex-4-enoic acid with K(m) 30-40 times that for phenylalanine. The maximum velocity for 2-amino-4-methylhex-4-enoic acid was only 30% of that for phenylalanine with the A. californica enzyme, but the maximum velocities for the two substrates were identical for the other four species. 3. 2-Amino-4-methylhex-4-enoic acid was not found in the protein of A. californica, so discrimination against this amino acid probably occurs in the step of transfer to tRNA, though subcellular localization, or subsequent steps of protein synthesis could be involved. 4. Crotylglycine, methallylglycine, ethallylglycine, 2-aminohex-4,5-dienoic acid, 2-amino-5-methylhex-4-enoic acid, 2-amino-4-methylhex-4-enoic acid, beta-(thien-2-yl)alanine, beta-(pyrazol-1-yl)alanine, phenylserine and m-fluorophenylalanine were substrates for pyrophosphate exchange catalysed by the phenylalanyl-tRNA synthetases of A. californica or A. hippocastanum. Allylglycine, phenylglycine and 2-amino-4-phenylbutyric acid were inactive.