The phosphorylation of tyrosine protein residues in spermatozoa was dependent on the semen of individual boars at different stages of the cryopreservation technology. Sperm proteins in the fresh semen of a boar with poor semen freezability (boar K) exhibited a higher content of phosphotyrosine residues compared to boars with better semen freezability (boars F and J). In the semen samples extended in a Kortowo 3 extender (K3) and cooled at 16°C, there was a marked increase in protein phosphorylation in the sperm proteins of boars with good semen freezability. This was manifested in the appearance of phosphoproteins with molecular weights of 17, 32, 43, 52, 63 and 78 kDa. In the case of boar K, the cooled-storage of K3-extended semen at 5°C caused the extensive phosphorylation of sperm proteins, with molecular weights of 45, 65 i 100 kDa. A gradual reduction in sperm protein tyrosine phosphorylation was detected in the extender containing lipoprotein fraction isolated from ostrich egg yolk (LPFo) compared with the K3 extender, what has no protective substances. It might be suggested that seminal plasma acid phosphatases, especially the vesicular molecular form of acid phosphatase (PTAP), played a very important role in the regulation of tyrosine phosphorylation in boar sperm plasmalemma proteins. Differences were observed in the number of dephosphorylated proteins by different molecular forms of phosphatases. It was shown that phosphotyrosine residues in sperm proteins could be completely dephosphorylated by the vesicular PTAP. It seemed that only sperm phosphotyrosine proteins, with molecular weights of 17, 32, and 63 kDa, could be dephosphorylated by the epididymal molecular form of acid phosphatase.
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