Ribonucleases and Deoxyribonucleases

The structure-activity relationships of bovine pancreatic ribonuclease I have been examined. About 90% of the enzymic activity was lost on modification of two thirds of the L-arginine residues with cyclohexanedione. 

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.  

---

Maruyama, T., Sonokawa, S. and Matsushitaa, H. Goto, M. (2007) Inhibitory effects of gold(III) ions on ribonuclease and deoxyribonuclease. Journal of Inorganic Biochemistry, 101, 180-186. 

In addition to the enzymes that catalyse the formation of nucleotides and polynucleotides, a large number of catabolic systems exist which operate at all levels of the internucleotide pathways. The ribonucleases and deoxyribonucleases that degrade polynucleotides are probably not significantly involved in purine analogue metabolism, but the enzymes which dephosphorylate nucleoside 5 -monophosphates are known to attack analogue nucleotides and may be of some importance to their in vivo activity. Phosphatases of low specificity are abundant in many tissues [38], particularly the intestine [29]. Purified mammalian 5-nucleotidases hydrolyse only the nucleoside 5 monophosphates [28] and... 

Nucleic acids are broken down into their components by nucleases from the pancreas and small intestine (ribonucleases and deoxyribonucleases). Further breakdown yields the nucleobases (purine and pyrimidine derivatives), pentoses (ribose and deoxyribose). 

In the small intestine, ribonuclease and deoxyribonuclease I, which are secreted in the pancreatic juice, hydrolyze nucleic acids mainly to oligonucleotides. The oligonucleotides are further hydrolyzed by phosphodiesterases, also secreted by the pancreas, to yield 5 - and 3 -mononucleotides. Most of the mononucleotides are then hydrolyzed to nucleosides by various group-specific nucleotidases or by a variety of nonspecific phosphatases. The resulting nucleosides may be absorbed intact by the intestinal mucosa, or they may un-... 

Finally, the activity of hydrolytic enzymes as ribonuclease and deoxyribonuclease was found to increase after in-vivo cadmium supply to Glycine max seedlings. These effects were considered as symptoms of cadmium accelerated senescence (Lee et al., 1976a see section on enzyme induction). 

Class 3. Hydrolases make use of water to cleave a single molecule into two molecules. They include esterases, glycosidases, peptidases, thiolases, phospholipases, amidases, ribonuclease, and deoxyribonuclease. 

Bacterial nucleic acids were hydrolyzed using bovine pancreatic ribonuclease and deoxyribonuclease.37 Deoxyribonuclease treatment of disrupted bacterial suspensions has also been reported.38... 

For effective removal of nucleic acids, both ribonuclease and deoxyribonuclease need to be used.29 The cost of nucleases is a major hindrance in use of this method in removal of nucleic acids from mixtures during protein purification. An organism s own nucleases may provide an often-unrecog-nized nuclease treatment. 

Ribonuclease from other mammalian sources may have several carbohydrate fragments in their structures. Thus, ribonuclease B from porcine pancreas contains at least three carbohydrate moieties, and these are attached9 at asparagine residues 21, 34, and 76. The carbohydrate moieties present at residues 21 and 76 are considerably more complex than that at residue 34, and their structures are under investigation in several laboratories. The carbohydrate portions of the isoenzymes of deoxyribonuclease are similar in structure to those from the ribonucleases.11 As ribonuclease and deoxyribonuclease originate in the same organ, it is possible that the same pathways and enzymes are utilized for the biosynthesis of the carbohydrate moieties of both enzymes. 

D3. Daoust, R., and Amano, H., Ribonuclease and deoxyribonuclease activities in experimental and human tumors on the histochemical substrate film method. Cancer Res. 28, 131-134 (1963). 

Steigleder, G. K., and Fissher, I., Localization of ribonuclease and deoxyribonuclease activity in normal skin, skin altered by inflammation and in skin tumors. Arch. Klin. Expil. Dermatol. 217, 653-562 (1963). 

In this chapter, we will focus on the present insights into the structure-activity relationship and the clinical situation of this enzyme without attempting to include all relevant studies. For reviews on the biochemistry up to 1980, we largely refer to the work of M. Laskowski [1], who was closely involved in the early studies on DNase I, and of S. Moore [9]. Moore shared with W. Stein the Nobel Prize in Chemistry in 1972 for their work on the chemical structures of pancreatic ribonuclease and deoxyribonuclease [10]. 

S. Moore and W. H. Stein. Chemical structures of pancreatic ribonuclease and deoxyribonuclease. Science 180 458-464 (1973). 

Moore, S. and W. Stein. 1972. The chemical synthesis of pancreatic ribonuclease and deoxyribonuclease. Nobel Lecture 80-93. 

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). 

C2 Caldarera, C. M. and Marchetti, M. Liver ribonuclease and deoxyribonuclease activity of vitamin B 12-deficient chicks effects of orotic acid and methionine. Nature (London), 195, 703-704 (1962)... 

Some enzymes are rendered inactive by specific or unspecific inhibitors, as in the case of ribonuclease and deoxyribonuclease. Other enzymes have latent activity because their active center is in some way inactivated by some polypeptidic chain in the molecule. Once the inhibiting chain has been removed by the action of proteolytic enzymes, the enzyme becomes fully active, as is the case for example, for thrombin and chymotrypsin. Finally, the activity of some enzymes is kept latent because of the absence of a cofactor e.g., phenylpyruvic hydroxylase in the developing liver). 

The turnover of nucleic acids is a continuous process in which synthesis and degradation are carefully regulated. Degradation of RNA and DNA are effected by a variety of ribonucleases and deoxyribonucleases respectively. The nucleotides are converted to nucleosides by the action of... 

---