Site of aromatic L-amino acid oxidase in dead bovine spermatozoa and determination of between-bull differences in the percentage of dead spermatozoa by oxidase activity

Abstract

Most (94%) of the aromatic L-amino acid oxidase activity in dead bovine spermatozoa was recovered in tail preparations. The enzyme was released from the cell in sodium citrate but not in sodium phosphate or sodium chloride solutions but oxidase activity was not significantly different in sodium phosphate or sodium citrate buffers (9.6 microliters O2/h and 11.2 microliters O2/h). The activity in ejaculated spermatozoa was correlated with the percentage of dead spermatozoa (r = 0.954, P less than 0.01) but could not be detected in freshly collected epididymal spermatozoa. Killed epididymal spermatozoa showed oxidase activity (10.1 microliters O2/h) similar to that of killed ejaculated spermatozoa (9.2 microliters O2/h). It is concluded that death of spermatozoa occurs in the ampulla and/or at ejaculation and that between-bull differences in the percentage of dead spermatozoa are a consequence of differences between bulls in conditions in the ampulla and/or at ejaculation.

Human spermatozoa possess an IL4I1 l-amino acid oxidase with a potential role in sperm function

“…All experiments run on three independent samples. a loss of plasma membrane integrity (Shannon & Curson 1982). This observation was confirmed with equine spermatozoa (Fig.…”

“…LAAO activity has also been observed in bull, ram, and stallion spermatozoa; however, the enzyme in human spermatozoa exhibits some notable differences with these species. In all other species analyzed, the enzyme has been found to exhibit an exclusive preference for aromatic amino acids (phenylalanine, tryptophan, and tyrosine; Tosic & Walton 1950, Shannon & Curson 1972, 1982, Upreti et al 1998. In human spermatozoa, tyrosine was not active as a substrate, but other nonaromatic L-amino acids (lysine, isoleucine, asparagine, and leucine) did exhibit a low level of activity (Fig.…”

“…Egg yolk-based cryodiluents have been shown to possess sufficient quantities of phenylalanine to stimulate LAAO activity and the generation of ROS by dead cells in the sperm suspension. The oxidative stress generated in this way has then been shown to compromise the functionality of live spermatozoa in the immediate vicinity (Shannon & Curson 1982). While activation of ROS generation by phenylalanine does ultimately compromise both the motility and the vitality of human spermatozoa (Fig.…”

“…This oxidase was found to have a particular propensity for the deamination of aromatic amino acids, with phenylalanine the preferred substrate (Tosic & Walton 1950). Subsequent studies have confirmed the presence of an LAAO in bull (Shannon & Curson 1972, 1982 and ram (Upreti et al 1998) spermatozoa with the potential to damage sperm function as a result of oxidative stress. The way in which exposure to hydrogen peroxide leads to a loss of sperm function has also been thoroughly investigated since the pioneering work of Tosic & Walton (1946), and shown to involve a number of pathological processes from the generation of cytotoxic aldehydes as a consequence of lipid peroxidation (Jones et al 1979, Aitken & Curry 2011, Aitken et al 2012 to the formation of potentially mutagenic base adducts in sperm DNA (De Iuliis et al 2009).…”

Discovery of Predictive Biomarkers for Litter Size in Boar Spermatozoa*

“…LAAO is a potential enzyme that is active after sperm cell death. To activate LAAO, the permeability of the membrane related to cell senescence and death is increased (51,52). Shannon and Curson (51) reported that LAAO is located in the bovine sperm tail.…”