Ribonuclease Activities and Distribution in Alzheimer''s and Control Brains

Levels of free and total alkaline ribonuclease, and levels of acidic ribonuclease, were measured postmortem in control brains and in the brains of patients with Alzheimer's disease. In each brain region assayed, whether control or Alzheimer's, there was a statistically significant difference between the levels of free and total alkaline ribonuclease. Between 59 and 90% of the enzyme activity was associated with alkaline ribonuclease inhibitor in an inactive complex. Levels of free and total alkaline ribonuclease varied widely among different brains and brain regions, and were always lower in cerebellum than in temporal cortex and occipital pole. There was no significant difference in the levels of total alkaline ribonuclease, free alkaline ribonuclease, or acidic ribonucleases between corresponding regions of Alzheimer's and control brains. There was also no qualitative difference in the subcellular distribution of the alkaline and acidic ribonucleases between Alzheimer's and control brain. No significant relationships were found between ribonuclease levels and age, neuritic plaque density, postmortem interval, or storage time.     

Mutants of Escherichia coli Lacking Endonuclease I, Ribonuclease I, or Ribonuclease II

To isolate mutants of Escherichia coli K-12 lacking endonuclease I activity (end), a method has been developed which detects, by differential methyl green staining, undegraded deoxyribonucleic acid (DNA) in colonies previously incubated in toluene. This procedure allows isolation of mutant strains in which DNA degradation is reduced. For half of these strains, this defect has been correlated with deficiencies of endonuclease I, ribonuclease I (rns), or ribonuclease II (rne) activities. The enzymatic deficiencies of the other strains remain unknown. An rne mutation is cotransducible with serA (which is located at 56 min on the genetic map). Most end mutations, called endA, are also cotransducible with serA and are located between serA and strA. One end mutation, called endB, is located between purE and trp (i.e., between 13 and 25 min on the genetic map).     

Ribonuclease and Chlorophyllase Activities in Senescing Leaves

The activities of two enzymes, ribonuclease and chlorophyllase were investigated during the senescence of leaves. Ribonuclease activities were measured in primary leaves of Phaseolus vulgaris, and related to the levels of nucleic acid, protein and chlorophyll. Similarly, changes in chlorophyllase activity during senescence of leaves of Raphanus sativus were measured and related to chlorophyll. During senescence the levels of each enzyme as well as its respective substrate declined. Retardation of senescence, by excision of young tissue from intact plants or by treatment of detached leaves with cytokinins resulted in a maintainace of both the substrate and enzyme levels. It was concluded that high levels of ribonuclease and chlorophyllase activity are not linked directly with the degradation of RNA and chlorophyll during leaf senescence.     

Biochemical and Cytochemical Evidence for the Polar Concentration of Periplasmic Enzymes in a “Minicell” Strain of Escherichia coli

A number of "surface" enzymes of Escherichia coli (i.e., among those selectively released by osmotic shock) all displayed higher specific activities in extracts of minicells than in extracts of typical rod forms; these enzymes included alkaline phosphatase, cyclic phosphodiesterase, acid hexose monophosphatase, 5'-nucleotidase, and ribonuclease I. In addition, alkaline phosphatase, cyclic phosphodiesterase, and acid hexose monophosphatase were cytochemically localized to regions of minicell periplasm that resembled reactive polar enlargements of the periplasm in rod forms. In contrast, a number of "internal" cytoplasmic enzymes (inorganic pyrophosphatase, beta-galactosidase, glutamine synthetase, polynucleotide phosphorylase, and ribonuclease II) showed elevated or similar specific activities in extracts of rod forms versus extracts of minicells. A specific heat-labile inhibitor for 5'-nucleotidase, known to occur in the cytoplasm, also showed no enrichment in minicells. These findings indicate that the "surface" enzymes are segregated in vivo into the terminal minicell buds, possibly because these enzymes are concentrated in the polar enlargements of the periplasm in typical rod forms.     

Bovine Brain Ribonuclease Is the Functional Homolog of Human Ribonuclease 1

Mounting evidence suggests that human pancreatic ribonuclease (RNase 1) plays important roles in vivo, ranging from regulating blood clotting and inflammation to directly counteracting tumorigenic cells. Understanding these putative roles has been pursued with continual comparisons of human RNase 1 to bovine RNase A, an enzyme that appears to function primarily in the ruminant gut. Our results imply a different physiology for human RNase 1. We demonstrate distinct functional differences between human RNase 1 and bovine RNase A. Moreover, we characterize another RNase 1 homolog, bovine brain ribonuclease, and find pronounced similarities between that enzyme and human RNase 1. We report that human RNase 1 and bovine brain ribonuclease share high catalytic activity against double-stranded RNA substrates, a rare quality among ribonucleases. Both human RNase 1 and bovine brain RNase are readily endocytosed by mammalian cells, aided by tight interactions with cell surface glycans. Finally, we show that both human RNase 1 and bovine brain RNase are secreted from endothelial cells in a regulated manner, implying a potential role in vascular homeostasis. Our results suggest that brain ribonuclease, not RNase A, is the true bovine homolog of human RNase 1, and provide fundamental insight into the ancestral roles and functional adaptations of RNase 1 in mammals.     

Ribonuclease activity of stressed tomato leaflets

Homogenates of leaflets of desiccated tomato plants show increased ribonuclease activity compared to homogenates of turgid controls. Much of this increase is independent of changes in translocation to and from the leaflet. Interruption of translocation through living cells by detachment of leaflets or steam damage to the petiolules produces increased ribonuclease activity, but this activity is increased further when excised leaflets are allowed to wilt. Increases in ribonuclease often parallel or precede increases in the soluble nitrogen content. Further increases in activity occur when excised leaves become yellow. Exposure of leaflets to CO₂-free air has little effect on activity at low-light intensity (120 ft-c). These results suggest that water stress directly affected ribonuclease activity at the cellular level.     

聚腺苷酸特异性核糖核酸酶(PARN)的功能多样性

聚腺苷酸尾的降解对于mRNA的质量控制和转录后基因调控十分重要. 在真核生物中,去腺苷酸化是mRNA降解和翻译沉默的首要限速步骤. 3′核糖核酸外切酶--聚腺苷酸特异性核糖核酸酶（poly(A)-specific ribonuclease,PARN）能够高效降解真核生物mRNA的聚腺苷酸尾. PARN不仅在降解mRNA poly(A)尾中发挥关键的作用,还参与DNA损伤、非编码RNA的加工成熟以及肿瘤等疾病过程. PARN是一种多功能酶分子,本文就PARN发现、结构、催化机制和功能多样性进行综述.     

Ribonuclease sensitivity of Escherichia coli ribosomes

Santer, Melvin (Haverford College, Haverford, Pa.), and Josephine R. Smith. Ribonuclease sensitivity of Escherichia coli ribosomes. J. Bacteriol. 92:1099-1110. 1966.-The ribonucleic acid (RNA) contained in 70S ribosomes and in 50S and 30S subunits was hydrolyzed by pancreatic ribonuclease. A 7% amount of the RNA was removed from the 70S particle; at 10(-4)m magnesium concentration, a maximum of 24 and 30% of the RNA in the 50S and the 30S fractions, respectively, was removed by ribonuclease. At the two lower magnesium ion concentrations, 50S ribosomes did not lose any protein, whereas 30S ribosomes lost protein as a result of ribonuclease treatment. A number of proteins were removed from the 30S particles by ribonuclease, and these proteins were antigenically related to proteins present in 50S ribosomes. The differential effect of ribonuclease on 50S and 30S ribosomes suggested that they have structural dissimilarities.     

Plant Nucleases: V. Survey of Corn Ribonuclease II Isoenzymes

Corn (Zea mays L.) ribonuclease II of the root microsomal fraction was isolated from 11 inbreds and seven hybrids. Polyacrylamide gel electrophoresis revealed a total of five bands of activity among corn lines tested. Most inbreds had only one isoenzyme, but three had two isoenzymes. The hybrids tested contained all of the isoenzymes found in the parental inbreds.     

Ribonuclease of cultured mammalian cells

KB cell ribonuclease has been purified 260-fold and the fundamental properties have been studied. Though the enzyme is concentrated in the lysosomal fraction, appreciable quantities are present in the cell sap and nuclear fractions. Comparison of the optimal temperature and pH for activity, and the heat stability of enzyme from these three fractions suggests that only one species of this enzyme exists in these cells. The enzyme behaves as an endonuclease, cleaving synthetic pyrimidine polynucleotides to smaller oligonucleotides with cyclic 2′:3′ end-groups. The final product is pyrimidine nucleoside 3′ monophosphate. Polyadenylic acid is not hydrolyzed. Of the properties examined in this study only two differences were noted between KB cell and pancreatic ribonuclease. KB cell enzyme acts optimally at pH 6 as opposed to an optimum at pH 7 to 8 for pancreatic enzyme. In addition ribonuclease from KB cells is definitely less stable to heating at 100°C than is the enzyme isolated from pancreas.     

Distribution of ATP-inhibited Ribonuclease in Bacteria

ATP-inhibited ribonuclease was first found in Bacillus amyloliquefaciens cells and was isolated by the authors previously. The distribution of the ATP-inhibited ribonuclease was surveyed on various bacteria. ATP-inhibited ribonuclease was found in only several species of Bacillus genus, i.e., B. subtilis (i), B. amyloliquefaciens (ii), B. cereus (iii), B. cereus var. mycoides (iv), and B. thiiringiensis (v). ATP-inhibited ribonuclease of Bacillus genus was subdivided into two types. The first type of enzyme found in (i) and (ii) cells had optimum pH at 5.7 and was sensitive to 5 mM EDTA. The second type of enzyme found in (iii), (iv), and (v) cells had optimum pH at 6.8 and was partially inhibited by 5 mM EDTA.     

Ribonuclease in the experimental therapy of pancreatitis

The influence of ribonuclease on the morphogenesis of experimental pancreatitis in the albino rats has been studied. The drug injected during edematous stage of pancreatitis caused some decrease of pancreatic enzymes level in the blood at hemorrhagic stage and its normalization at necrotic stage of pancreatitis. The development of hemorrhagic and necrotic stages of pancreatitis did not change under the influence of ribonuclease. The maturation of connective tissue of pseudocyst capsule was delayed and inflammatory infiltration of necrotic tissues and their elimination were increased under the influence of the drug. There were extensive tubular transformations of acini and early fibrosis and lipomatosis in the frontier zone. In the viable parts of pancreas moderate hypertrophy of exocrine pancreatocytes developed and chronic pancreatitis features appeared with use of ribonuclease.     

Ribonuclease III is involved in motility of Escherichia coli.

Mutants of Escherichia coli deficient in ribonuclease III are nonmotile. All transductants and revertants that regained ribonuclease III also regained motility, and all transductants that remained or became rnc are nonmotile, although only some of the revertants that regained motility also became ribonuclease III+.     

Ribonuclease in Leaves of Phaseolus vulgaris during Maturation and Senescence

The levels of the enzyme ribonuclease (RNase) were determined in primary leaves of Phaseolus vulgaris in an attempt to correlate changes in RNA with maturation and senescence. RNase, RNA and chlorophyll levels increased in expanding and maturing tissue and subsequently declined in senescing tissue. Senescence of the primary leaves started with the onset of flowering. A simultaneous increase of RNA and RNase in maturing tissue and a decrease during senescence suggests that the enzyme activity is correlated with the rate of‘turnover’of RNA rather than the absolute levels of RNA present in the tissue.     

Ribonuclease H activity present in purified DNA polymerase from avian myeloblastosis virus

The presence of ribonuclease H activity in the purified complex of DNA polymerase from avian myeloblastosis virus is described. Evidence includes co-chromatography of the two activities during all purification steps; the presence of ribonuclease H activity in the purified two-polypeptide complex of DNA polymerase; ion requirements for optimal activity of purified ribonuclease H are identical to those for the purified DNA polymerase; and monospecific antiserum against purified DNA polymerase neutralizes the ribonuclease H activity.     

Ribonuclease activity in preparations of human leukocyte interferon]

Preparations of human leukocyte interferon obtained by multi-stage purification procedure exhibited ribonuclease activity with the optimum at pH 7.0--7.5. The enzyme possessed the endonuclease action mechanism. Most substances studied for their effect on the RNA-ase activity in human interferon preparations showed many of them to act on the enzyme in the same way as on other ribonucleases. However, dithioerythritie, a reducing agent for disulfide bounds, activated the ribonuclease in the interferon preparation, as distinct from the pancreatic ribonuclease, which was inhibited by this preparation. Patterns of protein and RNA-ase distribution were obtained by electrophoresis in polyacrylamide gel.     

Ribonuclease Activity Associated With Ribosomes of Zea mays

At pH 6.5, a ribonuclease(s) is associated with ribosomes isolated from corn (Zea mays L.) and cannot be removed by repeated differential centrifugation or by sedimenting through the sucrose gradient. The enzyme is active under conditions favoring the maintenance of integrity of the ribosomes. Little or no latent ribonuclease appears to be present. The activity of the enzyme at pH 5.8 is stimulated by KCl and inhibited by polyvinyl sulfate, zinc, and bentonite. Deoxyribonuclease is also found on the particles.

The enzyme can be removed from ribosomes by adsorption onto bentonite. Ribosomes are also adsorbed but to a much lesser extent at low bentonite concentrations. The enzyme is easily dissociated from ribosomes by raising the pH to 8.5, and readsorbed when the pH is lowered.

The ribonuclease activity on ribosomes shows a sharp increase with cell age that parallels closely the increase in total activity in the homogenate. The ratio of activities of deoxyribonuclease to ribonuclease on ribosomes also changes with cell age and again the changes appear to reflect changes in the homogenate. It is suggested that most of the association of ribonuclease with corn ribosomes may not be meaningful in vivo and occurs only after the cells are ruptured.

     

核糖核酸酶5在宿主防御中的作用及机制

抗菌肽是机体天然免疫的重要组成部分。核糖核酸酶5（ribonuclease5,RNASE5;又名angiogenin）属于核糖核酸酶A超家族,是一个分泌型小分子蛋白质,广泛分布于机体需要抵御外界病原微生物的组织中。RNASE5对病毒、细菌以及真菌都存在抑制效应,具有广谱抗菌特点,但其表达和活性受到宿主生理状态和外界环境多层次的调控。RNASE5存在多样的抗微生物作用机制,其带正电荷的理化特性破坏微生物细胞壁,而其核糖核酸酶活性则是杀伤真菌所必须的。除了直接作用于微生物外,RNASE5还可作为重要因子调节宿主免疫功能,参与多种病理过程。本文综述了RANSE5的结构、生物活性与功能、作用特点与机制,并讨论了在其研究中存在的问题,以期为今后的研究提供新思路和新方向。     

Ribonuclease P

The gene coding for the RNA subunit of ribonuclease P (RNase P) is essential in all free-living organisms. The RNA subunit, itself, is an enzyme and, from its evolutionary tree, we can infer that it is a very ancient molecule. The specificity of this enzyme is that it cleaves other RNA molecules at the junction of single-stranded and the 5' end of double-stranded regions of RNA. One can speculate that this molecule was very useful in an ancient world in cleaving long pieces of RNA, which must have contained hairpin regions in it, into shorter molecules with the capability of different functions from the longer parent. Today, the specificity of the enzyme can be used in designing drug therapies.     

The Action of Ribonuclease on Fixed Tissues

To study the optimal conditions for histochemical use of ribonuclease on fixed tissues, the factors of (1) type of fixation, (2) temperature, pH, type of buffer and length of incubation, (3) concentration of enzyme, and (4) staining and dehydration of sections were observed on rabbit pancreas.

The fixing fluids studied were sublimate-alcohol, Bouin's, Zenker-acetic, Zenker-formol, Petrunkevich's cupric-paranitrophenol, 10% neutral formalin, SUSA, Carnoy, Bensley's chrom-sublimate, absolute ethyl alcohol and acetone. Formaldehyde was a satisfactory fixative, although others might be preferred for special purposes. Of the five buffers tested, McIlvaine's citric-acid-disodium-phosphate mixture was the most satisfactory, whereas veronal-acetate extracted considerable stainable cytoplasmic material. The optimum concentration of ribonuclease and length of incubation varied greatly after the 11 different types of fixation. For example, with ribonuclease buffered by Mcllvaine's fluid, the intense cytoplasmic staining of formaldehyde-fixed tissues was removed by concentrations as low as 0.001 mg./ml., whereas, with sections fixed in Zenkers fluid some cytoplasmic staining persisted even after 3 hours in 0.2 mg./ml. Under the conditions employed the temperature and hydrogen-ion concentration during incubation were less important. Examples of nonspecific action of ribonuclease were noted. Until the degree and optimum conditions of specific action have been more precisely established by further experiments, it is suggested that this histo-chemical reaction only be interpreted as a confirmatory test which is, under the best conditions, only relatively specific for ribonucleic acid and not highly quantitative.