Semenogelin is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that is involved in the formation of a gel matrix that encases ejaculated spermatozoa, preventing capacitation

Capacitation

Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte.This step is a biochemical event; the sperm move normally and look mature prior to capacitation....

. It blocks capacitation mainly via inhibition of reactive oxygen species

Reactive oxygen species

Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....

 (ROS) generation.

Proteolysis by prostate-specific antigen (PSA) breaks down the gel matrix and allows the spermatozoa to move more freely.

There are two variants of the semenogelin protein: Semenogelin 1 and Semenogelin 2.