Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.3 (RNase T1)
 1,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of polyamines on ribonucleases in the presence of various inhibitors (poly(G), heparin, and rat liver RNase inhibitor) has been studied. Bovine pancreatic RNas A and a ribonuclease from horse submaxillary gland (RNase HS) were inhibited by the inhibitors, but RNase T1 and RNase M were not inhibited. Polyamines were found to restore the activites of RNase A and RNase HS inhibited by poly(G) or heparin but not those activities inhibited by rat liver RNase inhibitor. When poly(U) and poly(C) were used as substrates, the inhibitory effects of poly(G) and heparin were greater with poly(U) than poly(C) as a substrate. However, when poly(C) was used as a substrate in the presence of either of the above inhibitors, the restoration of RNase activity by sperimine was more efficient. In fact, a stimulatory effect was observed. From the double-reciprocal plots, it was concluded that polyamines restored the activiities of RNases by increasing the availability of the substrate and enzyme to each other. The restoration of enzyme activity by polyamines occurred through the binding of the polyamines to the inhibitor and the subsequent release of enzyme from the inhibitor.
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PMID:Studies on the restoration of the activities of Ribonucleases by polyamines in the presence of various ribonuclease inhibitors. 40 77

Incubation of crude estrogen receptor preparations from mammary tumor cytosol with RNase A increases the sedimentation coefficient of the receptor from 9.7 S to 10.4 S. The effect is not obtained with other low molecular weight basic proteins (lysozyme, cytochrome c, or histone H2B). Nonenzymically active RNase A derivatives such as performic acid oxidized RNase A, fully reductively methylated RNase A, carboxymethyl-His-119-RNase A, and RNase S-protein were ineffective. RNase T1, an acidic endoribonuclease, was also without effect. However, enzymically active RNase S', prepared from a mixture of RNase S-protein and S-peptide, shifted the sedimentation to 10.4 S. The increased sedimentation is not accompanied by a change in the Stokes radius of the receptor (74 A) or buoyant density in metrizamide (1.24 g/ml). The effect of RNase A on the sedimentation of the receptor can be reversed by subsequent incubation with human placental RNase inhibitor or with rabbit anti-RNase A antibodies. Direct interaction was shown by chromatography of the receptor on RNase A Sepharose. Thus, the shift in sedimentation results from binding of RNase A to the receptor and, although this requires that the enzyme active site be available, enzymic activity is not responsible for the effect. The interaction of RNase A with the receptor occurs at low ionic strength; it does not occur at elevated ionic strength or after activation of the receptor by precipitation with ammonium sulfate.
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PMID:Interaction of ribonuclease A with estrogen receptor from rat mammary tumor MTW9. 683 88

The synthesis and enzymatic characterization of DUPAAA, a novel fluorogenic substrate for RNases of the pancreatic type is described. It consists of the dinucleotide uridylyl-3',5'-deoxyadenosine to which a fluorophore, o-aminobenzoic acid, and a quencher, 2,4-dinitroaniline, have been attached by means of phosphodiester linkages. Due to intramolecular quenching the intact substrate displayed very little fluorescence. Cleavage of the phosphodiester bond at the 3'-side of the uridylyl residue by RNase caused a 60-fold increase in fluorescence. This allowed the continuous and highly sensitive monitoring of enzyme activity. The substrate was turned over efficiently by RNases of the pancreatic type, but no cleavage was observed with the microbial RNase T1. Compared to the dinucleotide substrate UpA, the specificity constant with RNase A, RNase PL3 and RNase U(s) increased 6-, 18-, and 29-fold, respectively. These differences in increased catalytic efficiency most likely reflect differences in the importance of subsites on the enzyme in the binding of elongated substrates. Studies on the interactions of RNase inhibitor with RNase A using DUPAAA as a reporter substrate showed that it was well suited for monitoring this very tight protein-protein interaction using pre-steady-state kinetic methods.
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PMID:A novel fluorogenic substrate for ribonucleases. Synthesis and enzymatic characterization. 805 28

By reason of their cytotoxicity, ribonucleases (RNases) are potential anti-tumor drugs. Particularly members from the RNase A and RNase T1 superfamilies have shown promising results. Among these enzymes, Onconase, an RNase from the Northern Leopard frog, is furthest along in clinical trials. A general model for the mechanism of the cytotoxic action of RNases includes the interaction of the enzyme with the cellular membrane, internalization, translocation to the cytosol, and degradation of ribonucleic acid. The interplay of these processes as well as the role of the thermodynamic and proteolytic stability, the catalytic activity, and the capability of the RNase to evade the intracellular RNase inhibitor has not yet been fully elucidated. This paper discusses the various approaches to exploit RNases as cytotoxic agents.
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PMID:Natural and engineered ribonucleases as potential cancer therapeutics. 1690 46

Determining RNA structures (i.e., single- and double-strand regions) is often useful when assessing the potential for certain RNAs to interact with proteins or when determining whether RNAs that are dissimilar in sequence can form the same structure. A number of ribonucleases (RNases) have been used to map RNA structure, but many of these are no longer available. However, three commonly available RNA endonucleases (RNase T1, RNase I, and RNase V1) can provide a wealth of structural information. Cleavages of end-labeled RNA are initiated by one of the RNases (H2O is used for mock-treated controls), terminated with aurintricarboxylic acid (a potent RNase inhibitor), and detected by electrophoresis on denaturing polyacrylamide gels. Because there are enzymes that can cleave only when the RNA is single stranded (e.g., RNase T1) or double stranded (e.g., RNase V1), it is possible to do parallel analyses.
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PMID:RNA structure determination using nuclease digestion. 2354 52

Ribonucleases (RNases) are a large number of enzymes gathered into different bacterial or eukaryotic superfamilies. Bovine pancreatic RNase A, bovine seminal BS-RNase, human pancreatic RNase 1, angiogenin (RNase 5), and amphibian onconase belong to the pancreatic type superfamily, while binase and barnase are in the bacterial RNase N1/T1 family. In physiological conditions, most RNases secreted in the extracellular space counteract the undesired effects of extracellular RNAs and become protective against infections. Instead, if they enter the cell, RNases can digest intracellular RNAs, becoming cytotoxic and having advantageous effects against malignant cells. Their biological activities have been investigated either in vitro, toward a number of different cancer cell lines, or in some cases in vivo to test their potential therapeutic use. However, immunogenicity or other undesired effects have sometimes been associated with their action. Nevertheless, the use of RNases in therapy remains an appealing strategy against some still incurable tumors, such as mesothelioma, melanoma, or pancreatic cancer. The RNase inhibitor (RI) present inside almost all cells is the most efficacious sentry to counteract the ribonucleolytic action against intracellular RNAs because it forms a tight, irreversible and enzymatically inactive complex with many monomeric RNases. Therefore, dimerization or multimerization could represent a useful strategy for RNases to exert a remarkable cytotoxic activity by evading the interaction with RI by steric hindrance. Indeed, the majority of the mentioned RNases can hetero-dimerize with antibody derivatives, or even homo-dimerize or multimerize, spontaneously or artificially. This can occur through weak interactions or upon introducing covalent bonds. Immuno-RNases, in particular, are fusion proteins representing promising drugs by combining high target specificity with easy delivery in tumors. The results concerning the biological features of many RNases reported in the literature are described and discussed in this review. Furthermore, the activities displayed by some RNases forming oligomeric complexes, the mechanisms driving toward these supramolecular structures, and the biological rebounds connected are analyzed. These aspects are offered with the perspective to suggest possible efficacious therapeutic applications for RNases oligomeric derivatives that could contemporarily lack, or strongly reduce, immunogenicity and other undesired side-effects.
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PMID:Biological Activities of Secretory RNases: Focus on Their Oligomerization to Design Antitumor Drugs. 3184 26