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Peptidase activities in Crotalus durissus terrificus semen

C Marinho, Laboratory of Pharmacology, Instituto Butantan, Sao Paulo, Brazil
S Almeida Santos, Laboratory of Ecology and Evolution, Instituto Butantan, Sao Paulo, Brazil
S Carneiro, Laboratory of Cellular Biology, Instituto Butantan, Sao Paulo, Brazil
S Yamasaki, Laboratory of Pharmacology, Instituto Butantan, Sao Paulo, Brazil
P Silveira, Laboratory of Pharmacology, Instituto Butantan, Sao Paulo, Brazil

Correspondence: Paulo Silveira, Email: pefesil{at}butantan.gov.br

Abstract

To understand the role of peptidases in seminal physiology of Crotalus durissus terrificus, activity levels of representative enzymes in semen and their sensitivities to inhibitors, cofactors and peptide hormones were evaluated. The existence of seminal fractions and the association of peptidases with these fractions were also characterised for the first time in snakes. The prominent inhibitors of aminopeptidases were amastatin for acid, basic and neutral; bestatin for basic; and diprotin A for dipeptidyl-IV. Cystyl and prolyl-imino aminopeptidases were similarly susceptible to the majority of these inhibitors. The basic and neutral were characterised as metallo-peptidases, acid aminopeptidase was activated by MnCl2, and cystyl, prolyl-imino and type I pyroglutamyl were characterised as sulphydryl-dependent aminopeptidases. Angiotensin II, vasotocin, bradykinin, fertilization promoting peptide and thyrotropin-releasing hormone altered the majority of these peptidase activities; these peptides are possible substrates and/or modulators of these peptidases. Peptidase activities were found in all seminal fractions: seminal plasma, prostasome-like structures and soluble and membrane-bound fractions of spermatozoa. The levels of each peptidase activity varied among different seminal fractions. In seminal plasma the higher activities were puromycin-insensitive neutral and basic aminopeptidases. In prostasome-like, the higher activity was puromycin-insensitive neutral aminopeptidase. In spermatozoa, the higher activity in subcellular soluble fraction was puromycin-sensitive neutral, while in membrane-bound fraction both puromycin-sensitive and -insensitive neutral aminopeptidases were equally higher than the other examined peptidases. Data suggested that these peptidases, mainly basic and neutral aminopeptidases, have a high relevance in regulating seminal functions of C. d. terrificus.