In vitro penicillamine competition for protein-bound gold(I).

The reactions of penicillamine with gold sodium thiomalate (Myochrysine), gold-albumin complexes, and gold bound to urinary and kidney cytosolic proteins were examined. Large excesses of penicillamine (20 to 100:1 penicillamine/gold ratios) are required to mobilize significant amounts of protein bound gold. Quantitative comparisons of cysteine and penicillamine displacements of serum albumin bound gold indicate that penicillamine is approximately 5-6 times more effective than cysteine. Urinary gold is observed to be present in low molecular weight and protein bound forms, which exist in a labile chemical equilibrium and can be shifted by addition of penicillamine. These results are discussed in terms of the structure of gold(I)-penicillamine complexes and the distribution of gold(I) among protein and nonprotein thiol groups. The inappropriateness of using AuCl4- in vitro to study the biochemistry of chrysotherapy agents is delineated.