these results support the hypothesis that chronic , low level , arsenic exposure results in selective inhibition of mitochondrial-bound heme biosynthetic pathway enzymes ( ala synthetase and heme synthetase ) resulting in a substantial increase in urinary porphyrins , uniquely characterized by a greater increase in uroporphyrin than coproporphyrin levels .
C0032712
porphyrins
C0042093
uroporphyrin