Biochemical properties and kinetic parameters of monoamine oxydase in human seminal plasma

The present study demonstrates that monoamine oxydase (MAO) is present in the human seminal plasma and that its activity was higher in infertile than in fertile men. The Km and Vmax of the enzyme were, respectively, 3.0 X 10(-3) M and 625 eta mol of deaminated 5-HT mg of prot-1 min-1. The enzyme was activated by pyridoxal-5' phosphate but inhibited by usual MAO inhibitors such as pargyline-HCl, iproniazid-PO4 and clorgyline. These findings suggest a relationship between the synthesis and degradation of biogenic amines and testicular function.