Polyamines and polyamine-metabolizing enzyme activities in human semen

Abstract

The content of polyamines putrescine, spermidine and spermine as well as the activities of some polyamine-metabolizing enzymes have been analyzed from normal and pathological human semen samples. Seminal fluid from semen samples showing no apparent abnormalities in semen analyses contained about 0.2 mM of putrescine, 0.1 mM of spermidine and 3 mM of spermine. Seminal plasma was found to be an exceptionally rich source of diamine oxidase activity (EC 1.4.3.6). In addition, polyamine-synthesizing enzyme activities, S-adenosylmethionine decarboxylase and spermidine synthase, were invariably found in seminal plasma. Spermatozoa contained very low or undetectable activities of 5-adenosylmethionine decarboxylase and spermidine synthase; however, a definitive diamine oxidase activity was found also in the cellular component of the semen. The activity of diamine oxidase, and especially that of spermidine synthase, was relatively high in semen samples having low sperm density (less than 20 × 10 6 spermatozoa per ml). With increasing number of spermatozoa there was a slight decrease in both activities, but as the sperm count exceeded 100 × 10 6 per ml the activity of diamine oxidase and spermidine synthase sharply increased. The concentration of spermine in seminal plasma showed only minor changes in relation to the number of spermatozoa in semen, the changes being roughly opposite as compared to the changes of the enzyme activities. A significant negative correlation was found between the concentration of putrescine and the activity of diamine oxidase in seminal plasma. Several properties of diamine oxidase from human seminal plasma were found to be comparable to those of other mammalian diamine oxidases. Using radioactive putrescine as the substrate the enzyme activity was inhibited by addition of unlabelled histamine, cadaverine, spermidine and spermine. The enzyme was also powerfully inhibited by various carbonyl reagents and methylglyoxal bis-(guanylhydrazone).