This work forms part of the doctoral thesis of Bernd Wittig.
A New Acrosin Inhibitor from Boar Spermatozoa
Article first published online: 3 MAR 2005
European Journal of Biochemistry
Volume 126, Issue 1, pages 99–104, August 1982
How to Cite
TSCHESCHE, H., WITTIG, B., DECKER, G., MÜLLER-ESTERL, W. and FRITZ, H. (1982), A New Acrosin Inhibitor from Boar Spermatozoa. European Journal of Biochemistry, 126: 99–104. doi: 10.1111/j.1432-1033.1982.tb06752.x
- Issue published online: 3 MAR 2005
- Article first published online: 3 MAR 2005
- (Received February 25/April 20, 1982)
A new proteinase inhibitor (Mr 7500) was isolated to apparent homogeneity from boar spermatozoa by repeated gel filtration on Sephadex G-50 and affinity chromatography on concanavalin-A-Sepharose 4B. The inhibitor strongly inhibits boar acrosin in a competitive 1:1 stoichiometric reaction with a Kass= 7 × 1010l mol−1.
The inhibitor is a glycoprotein and represents a first member of a new class of proteinase inhibitor with a rather short polypeptide backbone of only 42 amino acid residues and a low cystine content. The basic protein (isoelectric point 9.4) contains a single disulfide loop, which is easily reducible by sodium borohydride. Upon reduction the inhibitory activity is lost, but rapidly regained after air reoxidation of the corresponding half-cystine residues. The reactive site residue was established to be arginine by inhibition with 2,3-butanedione. The inhibitor is rather specific for acrosin and inhibits bovine trypsin only to a limited extent. However, incubation with catalytic amounts of trypsin (or acrosin) at acid pH (pH 2–3) rapidly leads to a limited proteolysis at the reactive site with formation of 67% modified (reactive site hydrolysed), but still active inhibitor. The equilibrium constant was established to be Khyd= 2.0.