of the naturally occurring porphyrins the order of effectiveness is protoporphyrin ix ( dicarboxylic ) greater than coproporphyrin ( tetracarboxylic ) greater than uroporphyrin ( octacarboxylic ) and type i greater than type iii isomers of both uroporphyrin and coproporphyrin , and the synthetic tetra-meso-phenylporphinetetrasulphonate is a better inhibitor ( apparent ki = 250 nm ) than coproporphyrin , which contains a comparable number of negative charges .
C0032712
porphyrins
C0033733
protoporphyrin ix