Platelet-activating factor acetylhydrolase activity in bovine seminal plasma

Area of Science:

• Reproductive biology
• Enzymology

Background:

• Platelet-activating factor (PAF) is a signaling molecule found in mammalian sperm.
• Its function and production mechanisms, particularly in sperm, are not fully understood.
• PAF acetylhydrolase inactivates PAF and has been detected in human seminal plasma.

Purpose of the Study:

• To measure and characterize PAF acetylhydrolase in bovine seminal plasma.
• To investigate the enzyme's origin and properties.

Main Methods:

• Assay of PAF acetylhydrolase activity in seminal plasma, epididymal fluid, and sperm.
• Characterization of enzyme properties including linearity, cation dependence, and inhibition studies.
• Enzyme activity assessment in sperm before and after Percoll washing.

Main Results:

• Significant PAF acetylhydrolase activity detected in bovine seminal plasma (122 nmol/minute/mg protein).
• Activity was linear with time and protein concentration.
• The enzyme was cation-independent, unaffected by phosphatidylcholine, but inhibited by p-bromophenacylbromide and phenylmethylsulfonylfluoride.
• Minimal activity found in epididymal fluid/sperm; activity on ejaculated sperm was largely removed by washing.

Conclusions:

• Bovine seminal plasma possesses high PAF acetylhydrolase activity.
• The enzyme originates from accessory glands and shares properties with PAF acetylhydrolase from other sources.
• This enzyme likely plays a role in regulating PAF levels in the seminal environment.