Presence of a 16 kd protein in human seminal plasma counteracts the effects of the anti-fertility agent, gossypol.
Gossypol inhibited lactate dehydrogenase (LDH) noncompetitively in human spermatozoa. The inhibitory effect of gossypol on LDH was cancelled by the addition of human serum albumin, human gamma-globulin, bovine serum albumin or human seminal plasma. Seminal plasma was at least 10 times more effective than the other three proteins, when expressed on a per mg protein basis. Attempts were made to purify the active fraction from human seminal plasma. The purification steps included gel filtration, ammonium sulphate precipitation, centrifugal microconcentration and fast-performance liquid chromatography. A single active protein of Mr = 16,000 was purified to a final yield of 0.18%. The 16 kd protein was not observed in male blood plasma. The protein was found to be heat-stable and leucine-rich (16% of the molecule), and has been designated 'gossact'. The inhibitory effect of gossypol on the LDH reaction was completely blocked by the addition of gossact (5 micrograms/ml); human blood plasma (25 micrograms/ml) and human serum albumin (200 micrograms/ml) were far less potent in this assay. In addition, gossact bound 1.4 mol of gossypol/mol of protein with the dissociation constant (Kd) = 3.06 x 10(-5) M. The role of gossact in the protection of LDH from gossypol is discussed.
Nakamura
M
M
Department of Obstetrics and Gynaecology, School of Medicine, Teikyo University, Tokyo, Japan.
Ikeda
M
M
Komukai
M
M
Suyemitsu
T
T
Okinaga
S
S
Arai
K
K
D001667:Binding, Competitive; D006072:Gossypol / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000032:analysis / Q000037:antagonists & inhibitors; D008297:Male; D008970:Molecular Weight; D029584:Prostatic Secretory Proteins; D011487:Protein Conformation; D011506:Proteins / Q000302:isolation & purification*; D012661:Semen / Q000737:chemistry*; D029589:Seminal Plasma Proteins
D029584:Prostatic Secretory Proteins; D011506:Proteins; D029589:Seminal Plasma Proteins; C043076:beta-microseminoprotein; D007770:L-Lactate Dehydrogenase; D006072:Gossypol