The primary structure of calf chymosin

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Chymosin (rennin) is a key aspartic protease involved in milk clotting.
• Previous work established the primary structure of calf prochymosin's precursor segment.

Purpose of the Study:

• To determine the complete amino acid sequence of calf chymosin.
• To compare the sequence of calf chymosin with related enzymes to understand evolutionary and structural relationships.

Main Methods:

• Amino acid sequencing of calf chymosin.
• Bioinformatic comparison of primary structures with pig pepsinogen A and Penicillium janthinellum acid proteinase.

Main Results:

• The complete amino acid sequence of calf chymosin comprises a single peptide chain of 323 residues.
• The full calf prochymosin sequence (365 residues) was elucidated by combining new data with previous findings.
• Extensive sequence homology was observed between calf prochymosin and pig pepsinogen A (189 identical residues), and significant commonality with penicillopepsin (76 residues).

Conclusions:

• The determined amino acid sequence provides a comprehensive understanding of calf chymosin's primary structure.
• Sequence homologies strongly suggest that chymosin and other acid proteinases share similar peptide chain folding mechanisms.
• This research contributes to the comparative analysis of aspartic proteases and their evolutionary pathways.