Assertion: vampire's body | /r/Desires | porphyrin
Facets:
value: to produce heme
type: PURPOSE
Source sentences:
text: The body requires porphyrins to produce heme, which is used to carry oxygen in the blood among other things, but in the porphyrias there is a deficiency (inherited or acquired) of the enzymes that transform the various porphyrins into others, leading to abnormally high levels of one or more of these substances.