Dipeptidyl peptidase is a highly glycosylated serine protease with a broad tissue distribution. In the present study, we investigated the alteration of the activity of dipeptidyl peptidase of spermatozoa at different maturational levels in rat epididymis and the apparent correlation of enzyme activity with sperm forward motility. The maximum activity of the enzyme was observed in spermatozoa from the corpus or middle part of the epididymis. This glycyl-proline ρ-nitroanilide hydrolyzing enzyme of epididymal spermatozoa showed significant similarities with biochemical properties of dipeptidyl peptidase (DPP) type IV. Sitagliptin, a specific inhibitor of DPPIV, leads to a more effective and complete inhibition of the peptidase in spermatozoa collected from different parts of epididymis. The complete inhibition by Hg2+ and partial insensitivity toward Cd2+ also confirmed the similarities with ion sensitivity of DPPIV. Treatment of mature cauda spermatozoa with sitagliptin (1 mM) showed a significant inhibition in forward thrust in motility. This result suggests that sperm forward motility may be regulated by DPPIV-like enzyme of maturing epididymal spermatozoa.
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Mithun Shaw and Debjani Nath (2015) studied this question.
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