Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study confirms the previous reports that detergents can facilitate the reactivation of guanidinium chloride (GdmCl) denatured rhodanese (Tandon, S. and Horowitz, P. (1986) J. Biol. Chem. 261, 15615-15618; Tandon, S. and Horowitz, P. (1987) J. Biol. Chem. 262, 4486-4491). Here, we report the effect of the detergent, lauryl maltoside, on the reactivation of several enzymes other than rhodanese. For this study we used five different enzymes each having a single polypeptide chain, namely: adenosine deaminase; 3-phosphoglyceric phosphokinase; myokinase; 3 alpha-hydroxysteroid dehydrogenase; and phosphoglucomutase. The regain of enzyme activity was used to monitor refolding. Like rhodanese, these enzymes were denatured in 6 M GdmCl and diluted into a buffer containing various concentrations of lauryl maltoside. The effect of lauryl maltoside on reactivating these proteins depended on the specific enzyme used. For example, in the presence of lauryl maltoside, reactivation of adenosine deaminase increased to 98%, while phosphoglucomutase could not be reactivated significantly. The critical micelle concentration (CMC) of lauryl maltoside was measured under the present experimental conditions using 2-(p-toluidinyl)naphthalene 6-sulfonate (TNS) as an apolar fluorescent probe, and gave a value of 0.085 mg.ml-1 in 10 mM sodium phosphate (pH 7.4). The reactivating effect of lauryl maltoside was not generally related to its CMC. In some cases an induction period was observed before the enzyme attained its steady-state velocity. This might suggest the presence of intermediate(s) in the refolding pathway that could have been stabilized by the detergent. These findings indicate that 'non-denaturing' detergents may be useful for assisting reactivation of enzymes, although the optimum conditions will have to be determined for each individual case.
 ...
PMID:The effects of lauryl maltoside on the reactivation of several enzymes after treatment with guanidinium chloride. 338 70

The major purpose of these studies was to determine whether the expression of isozymes by tumor cells was heterogeneous among tumor cell subpopulations within a neoplasm and whether expression of one or another isozyme correlated with metastatic potential of tumor cells. The expression levels of 40 isozymes were determined in 56 cell lines, many of them clonal, from nine different murine and human tumors. The enzymes chosen for study are involved in nucleotide, carbohydrate and pentose phosphate metabolism, and as such are indicators of the general metabolic and differentiational status of the cell. The tumors studied included two murine and two human malignant melanomas, four murine fibrosarcomas, and one human prostatic adenocarcinoma. The lines isolated from these tumors consisted of cells that are tumorigenic non-metastatic, tumorigenic low metastatic and tumorigenic highly metastatic. Clonally derived cell lines from a given tumor differed in their expression of a number of different isozymes, including adenosine deaminase, creatine phosphokinase-B and lactate dehydrogenase. Different patterns of isozyme expression were observed among different tumor types as well as between tumors of the same type; however, there were no differences in isozyme expression for any enzyme tested that correlated with metastatic ability of tumor cells.
 ...
PMID:Heterogeneity of isozyme expression in tumor cells does not correlate with metastatic potential. 374 91

Previous work has shown that 6-thioguanine (TGua) is an effective inducer of differentiation of Friend and HL-60 leukemia cells which lack hypoxanthine-guanine phosphoribosyltransferase but is at best only weakly active in inducing maturation in parental wild-type cells. Studies in wild-type and mutant HL-60 cells have provided evidence that the free-base TGua is the form of this drug that induces differentiation, while the formation of TGua nucleotides leads to cytotoxicity and inhibits differentiation. To attempt to increase the potential of TGua to serve as an inducer of parental HL-60 leukemia cells, physiological purine and pyrimidine nucleosides were tested for their ability to protect HL-60 cells against TGua-induced cytotoxicity. Adenosine, deoxyadenosine, inosine, and deoxyinosine completely prevented the toxic action of the purinethiol, while guanosine and deoxyguanosine were only partially effective. The capacity of adenosine and deoxyadenosine to prevent the cytotoxicity of TGua was abolished by the inhibitor of adenosine deaminase, deoxycoformycin, implying that inosine and deoxyinosine were the active forms of the protecting agents. The protective activities of inosine and deoxyinosine appeared to depend on phosphorolysis catalyzed by purine nucleoside phosphorylase, since exogenously added hypoxanthine was as effective as inosine in reducing the cytotoxicity of the purine antimetabolite. Accumulation of TGua nucleotides in the acid-soluble fraction of HL-60 cells treated with TGua was significantly decreased by the presence of inosine. Inosine also served under these circumstances as a D-ribose 1-phosphate donor to TGua, as evidenced by its increased conversion to 6-thioguanosine. The prevention of the cytotoxicity of TGua by the simultaneous administration of hypoxanthine or its nucleosides resulted in an expression of the differentiation-inducing properties of TGua in HL-60 cells, as measured by the accumulation of nitroblue tetrazolium-positive cells. These findings support the concept that the processes of cytotoxicity and differentiation are separable events produced by different metabolic forms of the purine antimetabolite.
 ...
PMID:Enhancement of the differentiation-inducing properties of 6-thioguanine by hypoxanthine and its nucleosides in HL-60 promyelocytic leukemia cells. 385 87

The exact pathway whereby the initial catabolism of the adenine nucleotides proceeds from AMP and the possibility of a recycling of adenosine were investigated in human erythrocytes. Adenine nucleotide catabolism, reflected by the production of hypoxanthine, is very slow under physiologic conditions and can be greatly increased by suppression of glucose or alkalinization of the medium. Experiments with inhibitors of adenosine deaminase and adenosine kinase demonstrated that under physiologic conditions the initial catabolism of AMP proceeds by way of a deamination of AMP, followed by dephosphorylation of inosine monophosphate, and that no recycling occurs between AMP and adenosine. Under glucose deprivation, approximately 75% of the 20-fold increase of the catabolism of the adenine nucleotides proceeded by way of a dephosphorylation of AMP followed by deamination of adenosine, and a small recycling of this nucleoside could be evidenced. Inhibition of adenosine transport showed that the dephosphorylation of AMP occurred intracellularly. When the incubation medium was alkalinized in the presence of glucose, the 15-fold increase in the conversion of AMP to hypoxanthine proceeded exclusively by way of AMP deaminase but a small recycling of adenosine could also be evidenced. The threefold elevation of intraerythrocytic inorganic phosphate (Pi) during glucose deprivation and its 50% decrease during alkalinization as well as experiments in which extracellular Pi was modified, indicate that the dephosphorylation of red blood cell AMP is mainly responsive to variations of AMP, whereas its deamination is more sensitive to Pi.
 ...
PMID:Pathways of adenine nucleotide catabolism in erythrocytes. 394 80

The enzyme activities of cultured early erythroid progenitor cells (burst-forming unit erythroid, BFU-E) were measured and were compared with the activities of mature erythrocytes. The enzyme activity of acetylcholinesterase was not detectable in the erythroblasts. The ratios of phosphofructokinase and glutathione peroxidase were low due to low enzyme activities in both the erythroblasts and erythrocytes. The ratios of triose phosphate isomerase, phosphoglycerate kinase, and adenylate kinase were low due to high enzyme activities in both the erythroblasts and erythrocytes. The ratios of hexokinase, glucose phosphate isomerase, monophosphoglyceromutase, pyruvate kinase, and adenosine deaminase were high due to high enzyme activities in the erythroblasts. The isozyme of erythroblast hexokinase was of the prototype isozyme I, while pyruvate kinase was predominantly of the prototype M2, with two hybrid isozymes to the anodal side by electrophoresis. These facts suggest that there is a greatly different metabolic pattern during the maturation of the erythroid cells.
 ...
PMID:Enzyme activities of cultured erythroblasts. 403 55

The hydrolysis of adenosine 3'-monophosphate by serum acid phosphatase has been coupled to the liberation of ammonia from the adenosine generated through the action of exogenous adenosine deaminase. The ammonia is measured at the end of the incubation by a modification of the phenol-hypochlorite reaction of Berthelot. Optimum conditions for the enzyme reaction have been defined. Inhibition of the Berthelot reaction by the serum used in the assay is small, and may be compensated by a correction factor. Although the value for the control is high in relation to the test over the normal range, this is largely outweighed by the good sensitivity and precision of the method. The substrate is not significantly hydrolysed by erythrocyte acid phosphatase within the limits encountered in haemolysed sera. Experience of the method in routine hospital diagnosis compared favorably with that of a standard method employing disodium phenyl phosphate as substrate. It is suggested that activities greater than 3.1 IU/l should be further investigated and those greater than 3.7 IU/l should be regarded as definitely raised. The stability of human serum AcPase when promptly separated and held at 4 degrees C or - 20 degrees C was confirmed. At room temperature, acidification to pH 6.0 greatly improved stability.
 ...
PMID:Colorimetric determination of serum acid phosphatase activity using adenosine 3'-monophosphate as substrate. 410 91

To investigate the problem of initiation in bacterial spore germination, we isolated, from extracts of dormant spores of Bacillus cereus strain T and B. licheniformis, a protein that initiated spore germination when added to a suspension of heat-activated spores. The optimal conditions for initiatory activity of this protein (the initiator) were 30 C in 0.01 to 0.04 m NaCl and 0.01 m tris(hydroxymethyl)aminomethane (pH 8.5). The initiator was inhibited by phosphate but required two co-factors, l-alanine (1/7 of K(m) for l-alanine-inhibited germination) and nicotinamide adenine dinucleotide (1.25 x 10(-4)m). In the crude extract, the initiator activity was increased 3.5-fold by heating the extract at 65 C for 10 min, but the partially purified initiator preparation was completely heat-sensitive (65 C for 5 min). Heat stability could be conferred on the purified initiator by adding 10(-3)m dipicolinic acid. A fractionation of this protein that excluded l-alanine dehydrogenase and adenosine deaminase from the initiator activity was developed. The molecular weight of the initiator was estimated as 7 x 10(4). The kinetics of germination in the presence of initiator were examined at various concentrations of l-alanine and nicotinamide adenine dinucleotide.
 ...
PMID:Initiation of bacterial spore germination. 429 13

Supplementing the salts-glucose medium of Escherichia coli with adenine initiates induction of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4), growth inhibition, and an increased potential for the net deamination of adenine. The extent and duration of these events are proportional to the initial adenine concentration and are dependent upon adenylate pyrophosphorylase and repression of histidine biosynthesis for maximal expression. The conversion of adenine to hypoxanthine, though limited in rate, occurs concurrently with induction and accounts for the progressively decreasing rate of deaminase induction, since hypoxanthine is a relatively ineffective inducer. The subsequent decrease in deaminase activity is due to dilution by continued cell division and by enzyme inactivation which occurs during the late-log and early-stationary phases. The partially purified deaminase is labile to a number of environmental conditions, particularly to phosphate buffers of pH 6.8 or less. A disproportionately slow rate of adenine deamination by cells utilizing lactate permits a more prolonged period of induction and, consequently, a greater quantity of enzyme to be synthesized; cell division, but not enzyme inactivation, reduces enzyme concentration. The adenosine deaminases of Aerobacter aerogenes and Salmonella typhimurium are not inducible.
 ...
PMID:Induction of adenosine deaminase in Escherichia coli. 487 15

Purine-requiring mutants of Salmonella typhimurium LT2 containing additional mutations in either adenosine deaminase or purine nucleoside phosphorylase have been constructed. From studies of the ability of these mutants to utilize different purine compounds as the sole source of purines, the following conclusions may be drawn. (i) S. typhimurium does not contain physiologically significant amounts of adenine deaminase and adenosine kinase activities. (ii) The presence of inosine and guanosine kinase activities in vivo was established, although the former activity appears to be of minor significance for inosine metabolism. (iii) The utilization of exogenous purine deoxyribonucleosides is entirely dependent on a functional purine nucleoside phosphorylase. (iv) The pathway by which exogenous adenine is converted to guanine nucleotides in the presence of histidine requires a functional purine nucleoside phosphorylase. Evidence is presented that this pathway involves the conversion of adenine to adenosine, followed by deamination to inosine and subsequent phosphorolysis to hypoxanthine. Hypoxanthine is then converted to inosine monophosphate by inosine monophosphate pyrophosphorylase. The rate-limiting step in this pathway is the synthesis of adenosine from adenine due to lack of endogenous ribose-l-phosphate.
 ...
PMID:Metabolism of exogenous purine bases and nucleosides by Salmonella typhimurium. 492 5

Several isozymes have been evaluated by other investigators to help characterize both mycoplasmas and acholeplasmas. We have investigated a number of enzymes contributing to hypoxanthine production in Ureaplasma urealyticum, as part of an ongoing effort to identify a comparative profile of isozyme activities in this species. Cells from large volume cultures were collected by centrifugation and lysed by both freeze-thawing and sonication in hypotonic buffer with Triton X-100. Lysate was clarified by centrifugation. Proteins in the cell lysate were separated by polyacrylamide gel electrophoresis, incorporating Triton X-100 in the gel and electrode buffer. Gels were stained to indicate sites of hypoxanthine production from AMP, adenosine, inosine, or adenine, in either phosphate or Tris buffer. The results suggest that adenine deaminase, inosine nucleosidase, and adenosine phosphorylase activities are present in the cell lysate, while adenosine nucleosidase and adenosine deaminase activities are absent. Inosine phosphorylase, AMP nucleosidase and/or 5'-nucleotidase activities may also be present. With the formation of hypoxanthine, the possibility for a salvage pathway exists.
 ...
PMID:Enzyme activities contributing to hypoxanthine production in Ureaplasma. 609


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>