I.U.B.: 3.1.27.5

Pancreatic ribonuclease (RNase I) catalyzes cleavage of the phosphodiester bond between the 5'-ribose of a nucleotide and the phosphate group attached to the 3'-ribose of an adjacent pyrimidine nucleotide forming a 2',3'-cyclic phosphate which may then be hydrolyzed to the corresponding 3'-nucleoside phosphate. Ribonuclease A has a molecular weight of 13,700 daltons. It operates in an optimum pH range of 7.0-7.5.

Ribonuclease B has a molecular weight of 14,700 ± 300 daltons. It is a glycoprotein which possesses an amino acid composition indistinguishable from that of RNase A. It contains 6 residues of mannose and 2 residues of N-acetylglucosamine per molecule. It is a glycosylated derivative of RNase A.

Ribonuclease is inhibited by heavy metal ions and it is competitively inhibited by DNA. Since Molecular Biology Grade RNase A (Product Code: RPDF) is essentially free of DNase and protease activities, this product is useful in removing RNA from DNA in nucleic acid work and where other enzymes are used or where intact proteins must be recovered.

Stability/Storage: Molecular Biology Grade product (Product Code: RPDF) is stable at least 2 years at 2-8°C or -20°C. Other grades of RNase A and RNase B are stable 2-3 years at 2-8°C. R, RB, and RAF: Store at 2-8°C and protect from moisture. Product Code: RASE: Store at -20°C to maintain monomeric form. Product Code: RPDF: Store at 2-8°C or at -20°C.

Unit Definition: One Kalnitsky Unit causes an increase in absorbance of 1.0 at 260nm at 37°C and pH 5.0 when yeast ribosomal RNA is hydrolyzed to acid soluble oliognucleotides. One Kunitz unit equals 50 Worthington units.

Technical Notes: Special care should be given to handling of the enzyme because of its affinity for glass surfaces. The enzyme remains active but aggregates upon lyophilization and in solution at temperatures ≥2°C at low ionic strength. Heating solutions of RNase A to inactivate DNase may not be satisfactory since RNase activity may be lost if precipitate formation occurs and heat treated DNase may reactivate over time. Product Code: RPDF is suitable as supplied for applications requiring minimal DNase and protease levels and needs no further treatment. Product Code: RAF can be used without treatment in some applications. To heat-treat RAF, use 10mM acetate pH 5.0 with or without 15mM CaCl₂ for 15 minutes at 100°C or longer at 80°C. Product may precipitate if heated at neutral pH. Heat treatment of Product Code: RASE will precipitate product due to the presence of phosphate.

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