Mechanisms protecting plasma peptides from enzyme hydrolysis: a comparative study

Area of Science:

• Biochemistry
• Pharmacology
• Enzymology

Background:

• Plasma contains enzymes that hydrolyze peptides.
• Enkephalins are endogenous opioid peptides.
• The existence of substances protecting peptides from hydrolysis is known.

Purpose of the Study:

• To investigate the role of enkephalin-protecting plasma substances in shielding non-opioid peptides from enzymatic degradation.
• To compare the protective effects across different species and peptide substrates.

Main Methods:

• In vitro studies using plasma from laboratory animals and humans.
• Enzyme assays to measure peptide hydrolysis rates.
• Analysis of the protective effect of specific plasma fractions.

Main Results:

• Enkephalin-protecting substances effectively protected all examined peptides from plasma enzyme hydrolysis.
• The protective effect was generally uniform across species and peptides.
• Leucine enkephalin exhibited significantly higher protection in humans compared to other peptides and species.

Conclusions:

• Plasma contains substances that confer resistance to peptide hydrolysis.
• These protective substances may act by differentially inhibiting plasma aminopeptidases.
• The findings suggest a potential mechanism for regulating peptide stability in circulation.