Human pancreatic-type ribonucleases with activity against double-stranded ribonucleic acids

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Ribonucleases (RNAases) are crucial enzymes involved in RNA metabolism.
• The substrate specificity of RNAases, particularly their activity against double-stranded RNA (dsRNA), is of significant biological interest.
• Human pancreatic RNAase (Ribonucleate 3'-pyrimidino-oligonucleotidohydrolase, EC 3.1.4.22) is a well-characterized enzyme with potential roles in various physiological processes.

Purpose of the Study:

• To characterize the activity of human pancreatic RNAase against double-stranded RNA (dsRNA) compared to single-stranded RNA (ssRNA).
• To investigate the presence and activity of dsRNA-hydrolyzing RNAases in human serum and urine.
• To compare the dsRNA degradation capabilities of human pancreatic RNAase with those of other mammalian RNAases and RNAases from different human tissues.

Main Methods:

• Purification of acid-thermostable ribonuclease from human pancreas.
• Enzymatic assays measuring the hydrolysis rates of single-stranded and double-stranded RNA substrates.
• Comparative analysis of RNAase activity using crystalline ribonucleases from whale, rat, and cow, as well as purified RNAases from human spleen and liver.

Main Results:

• Human pancreatic RNAase degrades dsRNA at 2% the rate of ssRNA, indicating significant dsRNA hydrolytic activity.
• Human serum and urine contain pancreatic RNAase components with similar dsRNA degradation capabilities (2% and 0.4% of ssRNA rates, respectively).
• Other mammalian RNAases (whale, rat, cow) and human spleen/liver RNAases exhibit markedly lower relative activity against dsRNA compared to human pancreatic RNAase.

Conclusions:

• Human pancreatic RNAase is a potent enzyme capable of hydrolyzing dsRNA, a characteristic less pronounced in other tested RNAases.
• The presence of active dsRNA-hydrolyzing RNAase in human serum and urine suggests potential physiological roles or diagnostic relevance.
• The specific substrate preference of human pancreatic RNAase, including its activity against poly(C) in dsRNA and ssRNA, warrants further investigation.