Serum albumin and cyanide detoxication. Kinetic characterization of a reactive albumin-sulfur complex.

Kinetic studies of the serum albumin-catalyzed reaction of cyanide with colloidal elemental sulfur have been carried out to elucidate the formal mechanism of this reaction. The results indicate that one of the several sulfur-binding sites on the protein molecule is involved in a single displacement catalytic cycle in the presence of cyanide. At high velocities the rate of thiocyanate production is limited by an albumin-independent second order process which produces the form of sulfur that serves as substrate. The catalyzed reaction is also subject to substrate inhibition at high colloidal sulfur concentrations.