RIBONUCLEASE A

≥50 Kunitz u/mg

Molecular Weight: 13,700

Physical Description: White lyophilized powder

Source: Bovine pancreas

Composition: The composition and structure of ribonuclease A has been extensively investigated. The tertiary structure indicates that flexibility in a three-dimensional structure is essential for optimal catalytic activity. ^(2,3,4)

Optimum pH: 7.0 - 7.5 ⁽⁵⁾

Extinction coefficient: E^1%₂₈₀ = 7.3

Isoelectric point: pH 9.45 ⁽⁶⁾

Specificity: The enzyme is specific for pyrimidine nucleoside linkages, i.e., those cleaving cyclic 2',3'-pyrimidine nucleotide residues either singly or at the termination of purine nucleotide chains. ⁽⁷⁾

Inhibitors: Ribonuclease is inhibited by heavy metal ions and is competitively inhibited by DNA. The effect of denatured DNA is much greater than that of the native nucleic acid. ⁽⁸⁾

Stability: The enzyme is stable for years stored as a refrigerated dry powder or frozen in solution; refrigerated solutions are stable for weeks. The enzyme aggregates upon lyophilization and storage. ⁽⁹⁾ Special care should be given to handling of the enzyme because of its affinity for glass surfaces ⁽¹⁰⁾

Unit Definition: That amount of enzyme causing the hydrolysis of RNA at a rate such that k (velocity constant) equals unity at 25^oC and pH 5.0.

Non-specific protease activity: Not detectable.

Purity: >70%

Solubility: Dissolves readily at 2 mg/ml in analytical grade water to give a clear colorless solution.