Ribonuclease from cobra snake venom: purification by affinity chromatography and further characterization

Area of Science:

• Biochemistry
• Enzymology
• Toxicology

Background:

• Snake venom contains various enzymes, including ribonucleases (RNases) with diverse biological activities.
• Previous studies indicated cytidylic acid specificity for some snake venom RNases.

Purpose of the Study:

• To isolate and purify a ribonuclease from cobra snake venom.
• To characterize the enzyme's properties, including substrate specificity, optimal conditions, and structural behavior.
• To investigate its immunological relationship with other RNases and related proteins.

Main Methods:

• Antibody-affinity chromatography for enzyme purification.
• Enzyme activity assays to determine substrate specificity and effects of various conditions (pH, temperature, ions, inhibitors, urea).
• Salt-dependent association-dissociation behavior analysis.
• Immunological studies using antibody cross-reactivity.
• Partial N-terminal amino acid sequencing.

Main Results:

• A homogeneous ribonuclease was isolated from cobra venom with a fourfold increase in yield.
• The enzyme demonstrated specific activity towards cytidylic acid.
• Optimal activity was observed under specific conditions of temperature, pH, and metal ion concentration.
• The enzyme exhibited salt-dependent reversible association-dissociation.
• Immunological analysis revealed shared antigenic sites with Ribonuclease A.
• N-terminal sequencing showed homology with snake venom phospholipases, but no phospholipase activity was detected.

Conclusions:

• The purified cobra venom ribonuclease is a distinct enzyme with cytidylic acid specificity.
• Its unique salt-dependent behavior and antigenic properties provide insights into RNase evolution and function.
• Despite sequence homology, the enzyme lacks phospholipase activity, highlighting functional divergence.