Identification of the Second Form of Acrosin in Turkey Spermatozoa

Abstract

Acrosin from turkey spermatozoa has been recently identified and characterized. In this study, we reported the identification of second form of acrosin (acrosin II) in turkey spermatozoa. Using the three-step isolation procedure, we purified and characterized the acrosin II from a turkey spermatozoa extract. N-terminal Edman sequencing allowed the identification of the 24 amino acids from the internal part of acrosin II: SLQEYVEPYRVLQEAKVQLIDLNL. Thanks to homology alignment, we concluded that acrosin II is an acrosin-like protein similar to avian acrosin, including turkey acrosin. The molecular mass of acrosin II estimated by mass spectrometry was 30.869 kDa. During chromatofocusing, the acrosin II was eluted at pH range from 6.4 to 6.2. Acrosin II was found to be a glycoprotein. The glucosamine and galactosamine were present in carbohydrate structures of acrosin II. Acrosin II is characterized by similar physicochemical characteristics like previously identified bird acrosins, including acrosin from turkey spermatozoa. Similarities between turkey acrosins were also confirmed immunologically by western blot analysis. It can be suggested that two forms of serine proteinase similar to acrosin exist in turkey spermatozoa. These phenomena of both acrosins in spermatozoa agree with the concept of functional redundancy of proteolytic enzymes in the reproductive system. These redundancies may be important for efficient fertilization in turkey.