Competitive partial inhibitors of serum albumin-catalyzed sulfur cyanolysis.

Efforts to locate the active site for sulfur cyanolysis catalyzed by bovine serum albumin have led to systematic tests of several compounds that inhibit the catalyzed reaction. Hexanoate and 5-dimethylaminonaphthalene-1-sulfonate bind at the same site and are partial inhibitors competitive with cyanide, uncompetitive with respect to sulfur. Various dansyl amino acids and 1-anilino-8-naphthalene sulfonate display the same inhibitory behavior but bis (1-anilino-8-naphthalene sulfonate) is a total inhibitor competitive with cyanide. These findings are interpreted to indicate that the cyanolysis active site is near, but not at, one of the short-chain fatty acid binding sites on albumin subdomain 2-AB or 3-AB. Both ionic repulsion and steric considerations are implicated in the mechanisms of inhibition.