Dipeptidyl carboxypeptidase from human seminal plasma

Area of Science:

• Biochemistry
• Enzymology

Background:

• Dipeptidyl carboxypeptidase, or angiotensin I converting enzyme (ACE), is a key enzyme in the renin-angiotensin system.
• ACE has been extensively studied in lung tissue, but its presence and properties in other biological fluids are less characterized.

Purpose of the Study:

• To purify and characterize dipeptidyl carboxypeptidase from human seminal plasma.
• To compare the properties and substrate specificity of seminal plasma ACE with those of the well-characterized lung ACE.

Main Methods:

• Purification of the enzyme from human seminal plasma using gel filtration (Sephadex G-200) and isoelectric focusing.
• Determination of enzyme properties including relative molecular mass, isoelectric point (pI), optimal pH, and cofactor requirements (chloride activation).
• Enzyme activity assays using various synthetic and natural peptide substrates to determine specificity.

Main Results:

• Dipeptidyl carboxypeptidase was successfully purified from human seminal plasma.
• The purified enzyme exhibited an apparent relative molecular mass of 330,000, a pI of 4.6-5.0, and an optimal pH of 7.7-8.0.
• The enzyme demonstrated carboxypeptidase activity, releasing dipeptides, and was activated by chloride, showing similarities to human lung ACE. Substrate specificity studies indicated highest activity with Z-Leu-Gly-Gly.

Conclusions:

• Human seminal plasma contains a dipeptidyl carboxypeptidase (angiotensin I converting enzyme) with biochemical and catalytic properties similar to the lung enzyme.
• The characterization of seminal plasma ACE provides insights into its potential roles in reproductive physiology and its broader distribution in the human body.