Acrosin is a digestive enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that acts as a protease

Protease

A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....

. In humans, acrosin is encoded by the ACR gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

. Acrosin is released from the acrosome

Acrosome

The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa of many animals. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation. In Eutherian mammals the acrosome contains digestive enzymes...

 of spermatozoa as a consequence of the acrosome reaction

Acrosome reaction

During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem, whereas penetrating through the egg's hard shell can present more of a problem to the sperm...

. It aids in the penetration of the Zona Pellucida

Zona pellucida

The zona pellucida is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but of essential importance to it...

.

Function

Acrosin is the major proteinase present in the acrosome of mature spermatozoa. It is a typical serine proteinase with trypsin-like specificity. It is stored in the acrosome in its precursor form, proacrosin. The active enzyme functions in the lysis of the zona pellucida, thus facilitating penetration of the sperm through the innermost glycoprotein layers of the ovum. The mRNA for proacrosin is synthesized only in the postmeiotic stages of spermatogenesis. In humans proacrosin first appears in the haploid spermatids.

External links

• The MEROPS
  Merops
  Merops may refer to:* Merops , a genus of bee-eaters.* MEROPS, an on-line database for peptidases.It may also refer to several figures from Greek mythology:* King of Ethiopia, husband of Clymene, who lay with Helios and bore Phaethon...
  
  online database for peptidases and their inhibitors: S01.223