Deoxy-ribonucleases

The use of isolated enzymes to form or cleave P-O bonds is an important application of biocatalysts. Restriction endonucleases, (deoxy)ribonucleases, DNA/ RNA-ligases, DNA-RNA-polymerases, reverse transcriptases etc. are central to modern molecular biology(1). Enzyme catalyzed phosphoryl transfer reactions have also found important applications in synthetic organic chemistry. In particular, the development of convenient cofactor regeneration systems has made possible the practical scale synthesis of carbohydrates, nucleoside phosphates, nucleoside phosphate sugars and other natural products and their analogs. This chapter gives an overview of this field of research. 

DNA is not normally broken down, except after cell death and during DNA repair. RNA is turned over in much the same way as protein. The enzymes involved in breaking down both types of polynucleotides are the nucleases, or more specifically deoxy-ribonucleases and ribonucleases, they hydrolyze DNA and RNA, respectively, to oligo-nucleotides which can be further hydrolyzed (Fig. 14-38) so eventually purines and pyrimidines are formed. 

Rabbit immunoglobulin IgG anti-(deoxy-ribonuclease) antibody Rabbit immunoglobulin IgG anti-(human type-0) antibody... 

List of Abbreviations PCR, polymerase chain reaction RT-PCR, reverse transcription polymerase chain reaction DNA, deoxyribonucleic acid RNA, ribonucleic acid RNase, ribonuclease mRNA, messenger RNA GABAa, y-aminobutyric acid type A cRNA, copy RNA dNTPs, deoxy nucleoside triphosphates MMLV, Mouse Moloney murine leukemia vims RT, reverse transcriptase bp, base pair Tm, melting temperature DEPC, diethylpyrocarbonate OD, optical density mL, milliliter SA-PMPs, streptavidin paramagnetic particles dT, deoxy thymidine DTT, dithiothreitol DNase, deoxyribonuclease RNasin, ribonuclease inhibitor UV, ultraviolet TBE, Tris-borate, 1 mM EDTA EDTA, ethylenediaminetetraacetic acid Buffer RET, guanidium thiocyanate lysis buffer PBS, phosphate buffered saline NT2, Ntera 2 neural progenitor cells... 

Quercetin Rp 75 Fr cno Quinic acid RtDC240 Rhamnose Rt 200 Ribonuclease, deoxy Ppci65... 

Ribonuclease, deoxy P1NT576 Ribonuclease P1NT576 Rishitin ... 

A number of other proteins are now known to exhibit heterogeneity with respect to their carbohydrate content these include pig pancreatic ribonuclease,9 rabbit19 and human109-238 -yG immunoglobulin, ceruloplasmin,239 2-acetamido-2-deoxy-/3-D-glucosidase,240 and the blood-group substances from ovarian cysts.145,241... 

Syntheses have been reported for a number of glycopeptide derivatives containing the JV -(2-acetamido-2-deoxy-/J-D-glucopyranosyl) hydrogen L-asparagin-ate linkage and having the amino-acid sequences 32-34, 33-35, 33-37, and 33-38 of bovine ribonuclease. ... 

The 2,5-anhydro-3,4-diamino-pentose diethyl acetal 72 was synthesized from L-xylose by sequential reaction of epoxide and triflate intermediates with azide ion. After reduction to a 3,4-diamino-2,5-anhydroalditol, oxoruthenium(V) complexes of it and related 2,3-diamino-nucleosides (see Chapter 17) were prepared and evaluated as ribonuclease inhibitors. A number of routes were investigated for the preparation of the 2-amino-3-azido-2,3-dideoxy-D-glucoside 73, a precursor for a mimetic of the cyclopdepsipeptide didemnin B, from 2-acetamido-2-deoxy-D-glucose. Because A -deacetylation was much easier in the presence of a free 3-hydroxy-group, the best route involved preparation of a 2-deoxy-2-trifluoroacetamido-D-allopyranoside, and displacement of a mesylate group from C-3 by azide ion with inversion. ... 

The oxorhenium(V) complex 80 has been prepared from 2, 3 -diamino-2, 3 -dideoxyadenosine, and exists as a 2 1 mixture of syn- and an/i-isomers. Both were inhibitors of purine-specific ribonuclease, with the 57/i-isomer being more effective. " The same group has described a route to 3, 5 -diamino-3, 5 -dideoxy-adenosine (82) from the /> xo-epoxide 81 (Vol. 25, p. 251-2), as outlined in Scheme 10. The Mitsunobu inversion using benzyl alcohol as nucleophile is noteworthy, and proved superior to other strategies. An oxorhenium(V) complex was also formed from 82." Thymidine can be converted into the anhydronucleo-side 83 by two successive Mitsunobu reactions, and 83 was converted into the aminoderivative 84 of AZT, and some phosphoramidates were produced from 84." Some 5 -deoxy-5 -sulfonylamido derivatives of AZT have also been produced by successive displacements at 0-5 and 0-3 by nitrogen nucleophiles." ... 

During digestive processes, nucleoprotein is split into nucleic acids and protein, the latter then being broken down into amino acids. The nucleic acids are attacked by ribonuclease and deoxyribonuclease enzymes to form nucleotides, which are further hydrolysed by nucleotidases to form nucleosides and phosphates. In the intestines these nucleosides are split by nucleosidases into ribose, deoxy-ribose, purine and pyrimidine bases, which later undergo oxidation and decomposition to ammonia, carbon dioxide and water, to be finally expelled as urea. Nucleotide hydrolysis products are conveniently identified and isolated by chromatographic methods (Chapter 14.2). 

Signals in the aromatic region of the n.m.r. spectrum of colipase have been assigned to L-histidine residues. L-Histidine C-2 proton signals have been used in studies of the binding to ribonuclease A of H, edta and of 2 -deoxy-2 -fluorouridilyl-(3, 5 )-adenosine. L-Phenylalanine, L-tyrosine, and methionine side-chain proton resonances were used as monitors for the unfolding and stabilization of ribonuclease." ... 

Ribonuclease A.—Lactose has been coupled to L-lysine residues in the cross-linked dimer of bovine pancreatic ribonuclease A by reductive amination with cyanoborohydride. Derivatives of the dimer containing up to ten deoxy-lactitoyl)-L-lysine residues per molecule retained more than 75% of the activity of the native enzyme. The effect of modification of the enzyme on hepatic uptake was investigated. 

Miscellaneous.—An e db-j8-D-acetamidodeoxyglucanase obtained from culture filtrates of Streptomyces griseus rapidly released oligosaccharides from Saccharo-myces cerevisiae )8-fructofuranosidase, bovine pancreatic ribonuclease I and deoxyribonuclease 1, and sulphitolysed ovalbumin these glycoproteins contain a D-mannopyranosyl residue attached to di-iV-acetylchitobiose, which, in turn, is linked to an L-asparagyl residue. Analysis of the hydrolysis products showed that the enzyme cleaved between the 2-acetamido-2-deoxy-D-glucopyranosyl residues. 

The oligosaccharide chains of bovine pancreatic ribonuclease I and deoxyribonuclease I have been cleaved, using a specific e/idb-jS-D-acetamidodeoxy-glucanase, although one of the two 2-acetamido-2-deoxy-D-glucopyranosyl residues was not detached from the protein chain. ... 

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