Two kinins formed by trypsin from human plasma protein

Area of Science:

• Biochemistry
• Pharmacology

Background:

• Human plasma protein fraction IV-4 is a source of biologically active peptides.
• Trypsin is a protease known to cleave peptide bonds.

Purpose of the Study:

• To investigate the generation and characterization of depressor substances from human plasma protein fraction IV-4 by trypsin.
• To identify the chemical structure and biological activity of these depressor substances.

Main Methods:

• Enzymatic digestion of plasma protein fraction IV-4 with trypsin.
• Purification using gel-filtration, ion retardation chromatography, and partition chromatography.
• High-pressure liquid chromatography (HPLC) and thin-layer electrophoresis for separation and identification.
• Amino acid analysis and biological activity assays (oxytocic and potentiating activities).

Main Results:

• Trypsin generated depressor substances across a wide pH range (2.0-10.0).
• Two main depressor substances were isolated and identified.
• Substance 1, generated at pH 3.2, was identified as [des-Pro3]-bradykinin based on amino acid composition, HPLC retention time, and biological activity.
• Substance 2 was identified as bradykinin.

Conclusions:

• Trypsin effectively cleaves human plasma protein fraction IV-4 to produce bradykinin and its analog, [des-Pro3]-bradykinin.
• These identified peptides possess significant depressor and potentiating activities.
• The study elucidates the enzymatic generation of kinins from plasma precursors.