Characteristics of sperm acrosin-like activity of paddlefish ( Polyodon spathula Walbaum)

Abstract

Spermatozoa of paddlefish and sturgeon fishes ( Acipenseriformes), unlike teleost fish, have an acrosome. The objectives of this study were to characterize acrosin-like activity of cryopreserved sperm of paddlefish ( Polyodon spathula) and to test and compare stability of paddlefish acrosin-like activity with that of lake sturgeon and bull spermatozoa. Mean acrosin-like activity of cryopreserved paddlefish sperm was 0.372±0.067 μU/10 6 spermatozoa. This activity was 79% higher in the whole semen than in spermatozoa. Highest activity was recorded at pH 8.0 and 8.5. Triton X-100, zinc ions and 4′-acetamidophenyl 4-guanidinobenzoate (AGB) inhibited the activity. Amidase activity was also inhibited by N-α- p-tosyl- l-lysine chloromethyl ketone (TLCK) and N-tosyl- l-phenylalanine chloromethyl ketone (TPCK). TLCK at concentrations of 0.1 and 1.0 mM gave a significant decrease in activity of 19 and 61%, respectively. However, TPCK significantly inhibited amidase activity (by 19%) only at concentration 1.0 mM. After acidification and 60 min incubation at 4°C of sperm suspensions only 4% of the activity was retained. A similar phenomenon was observed in the case of lake sturgeon but not bull sperm. These results suggest that trypsin-like activity of Acipenserid fish resembles rather fish trypsin that mammalian one. In frozen–thawed paddlefish sperm a minute chymotrypsin-like activity was also indicated, when GPNA was used as substrate. This activity amounted to 0.0415±0.0138 μU/10 6 spermatozoa and was 18% of total amidase activity. This suggests that chymotrypsin-like activity may also be present in paddlefish spermatozoa.