Data on expression patterns of carboxylesterases in the male reproductive
tract of different animal groups (i.e. bivalve mollusks, fruitflies and
rodents) are summarized to highlight some particularly interesting questions
in the context of sperm differentiation, maturation and function. The male
reproduc-tive system, in spite of extreme variation in the
anatomical/morphological organization in different species, is
characterized by similar patterns of male-dependent carboxylesterase
overexpression. The phenomenon of conserved carboxylesterase overexpression
indicates similar male sex-associated functions of the enzymes. There is
possible evidence of carboxylesterase recruitment by male reproductive-tract
tissues indi-cating that it could be adaptive for spermatogenesis, sperm
maturation and sperm use. Moreover, this idea can be extended to include a
sperm cell lineage protection. This issue is discussed in the light of recent
data on environmental reproductive xenobiotics that can provide a basis for a
hypothetical explanation of car-boxylesterase overexpression in the male
reproductive tract. Based on a well-known role of car-boxylesterases in
detoxification of environmental chemicals such as organophosphate pesticides,
it is proposed that various male genital tract carboxylesterases may be
characterized by a similar physiological function to protect the male
reproductive system against xenobiotic influences that could provoke its
dys-function, thus altering sperm differentiation and maturation.
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