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. Uninary 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.