Reduction of porphyrins to porphyrinogens with palladium on carbon

Porphyrinogens serve as substrates for three heme biosynthetic enzymes. Porphyrinogens are highly unstable and must be generated as an integral part of enzyme assays. Methods commonly employed to generate porphyrinogens include chemical reduction using sodium amalgam or sodium borohydride and enzymatic generation from porphobilinogen. Chemical reduction yields porphyrinogens in highly alkaline solutions with high ionic strength, whereas enzymatic generation requires purified enzymes, deproteination, and complete buffer replacement. This article describes an improved method for reducing porphyrins to porphyrinogens using palladium on carbon as a catalyst under hydrogen at ambient temperature and pressure in the dark. The palladium catalyst is removed by filtration, the filtrate is blown dry with an inert gas, and the dried porphyrinogen can be dissolved in a buffer compatible with biological studies.