Mechanism of action of oxidized polyamines on the metabolism of human spermatozoa

Summary.Oxidized spermine, an iminoaldehyde (N,N′-bis(3-propionaldehyde) 1,4-diaminobutane), is a non-competitive inhibitor of fructolysis by human spermatozoa. The inhibition constant is about 0·3 mm. In experiments with [U-14C]fructose the iminoaldehyde caused a more pronounced depression of the formation of CO2than of lactate. The iminoaldehyde was without influence on the conversion of fructose to lactate by cell-free extracts of spermatozoa, but it markedly decreased the uptake of fructose and lactate by spermatozoa. These findings strongly suggest that inhibition of the fructose metabolism of intact spermatozoa was due to interaction of the iminoaldehyde with sperm membranes and not to inhibition of any enzyme of the glycolytic pathway. Several aliphatic and aromatic aldehydes were also tested for their ability to inhibit sugar utilization of human spermatozoa: only n-hexanal exerted an inhibitory effect, the extent of which approached that of oxidized spermine.