Two human trypsinogens. Purification, molecular properties, and N-terminal sequences.

Area of Science:

• Biochemistry
• Proteomics
• Human Physiology

Background:

• Human pancreatic juice contains precursor forms of trypsin, known as trypsinogens.
• Understanding these precursors is crucial for comprehending protein activation pathways in digestion.

Purpose of the Study:

• To isolate and characterize the molecular and structural properties of two distinct human trypsinogen forms.
• To compare their purification, protein yield, physicochemical properties, and activation mechanisms.

Main Methods:

• Purification of human trypsinogens using Sephadex G-100 filtration and DEAE-cellulose ion-exchange chromatography.
• Analysis of molecular weights, amino acid compositions, N-terminal sequences, and immunological identity.
• Characterization of activation peptides released during conversion to trypsin.

Main Results:

• Two human trypsinogen forms were isolated, constituting 19% of pancreatic juice proteins.
• Trypsinogen 1 is the major form, twice the quantity of trypsinogen 2, the most anionic protein.
• Both forms show partial immunological identity, similar molecular weights (23,438 Da and 25,006 Da), and amino acid compositions, with identical N-terminal sequences.
• Differences were observed in the activation peptides: trypsinogen 2 releases an octapeptide, while trypsinogen 1 releases the octapeptide and a pentapeptide.

Conclusions:

• Human pancreatic juice contains at least two distinct trypsinogen forms with unique activation pathways.
• These findings contribute to understanding trypsinogen heterogeneity and its implications in pancreatic function.