Platinum complexes and pyruvate kinase activity

The interaction of platinum complexes with bovine heart pyruvate kinase (PK) was studied by absorption, CD, fluorescence spectroscopy and enzymic activity test. Our results showed that activity of PK was reduced by cis-DDP and potassium tetrachloroplatinate in a time-and concentration dependent manner. Cis-DDP was less effective than K2PtCl4 in reducing PK activity. The native enzyme showed well defined negative Cotton effect at 222 and 208 nm indicating the presence of alpha-helical and beta structure. Platinum binding lowered the Cotton effect in this region by about 10-20% and 30-50% for the system with cis-DDP and K2PtCl4, respectively. Fluorescence study showed that platinum binding quenched tryptophan fluorescence suggesting that binding occurs at the tryptophan residue or its proximity. PK modifications induced by platinum binding would result in a greater resistance to denaturing agents.