Figure 7. Effect of PPi on proteasomal enzymatic activities of stored boar spermatozoa.

Fresh boar spermatozoa were stored in BTS with/without 10 µM PPi for 3 or 10 days (No treat/PPi+BTS). Proteasomal proteolytic and deubiquitinating activities were measured using specific fluorometric substrates Z-LLE-AMC (A), Z-LLVY-AMC (B), Z-LLL-AMC (C) and ubiquitin-AMC (D). In a separate treatment group, PPi (10 µM) was added before measurement to spermatozoa preserved without PPi in BTS (PPi). The emitted fluorescence (no units) was measured at multiple time points to follow the kinetics of the reaction (Excitation 380 nm; emission 460 nm). Experiments were repeated three times. Values are expressed as the mean of fluorescence intensity ± SEM.