Antipain is an oligopeptide that is isolated from actinomycetes and used in biochemical research as a protease inhibitor of trypsin and papain.

[5] In both cases, the backbone carbonyl of the terminal arginine of antipain forms a covalent bond to the active site serine in the protease.

A study was performed for information on the effect of antipain on the quality of post-thawed ram semen.

[6] The results from this experiment concluded that antipain aided in the quality of ram semen by maintaining the sperm mobility.

[6] Antipain includes the function to inhibit a degrading enzyme, called plasmin, permitting this substance to be able to improve the resistance of membrane disruption by freezing temperatures.