CREATE TABLE table_79167 ("Enzyme" CLOB, "Location" CLOB, "Substrate" CLOB, "Product" CLOB, "Chromosome" CLOB, "OMIM" FLOAT, "Porphyria" CLOB)

What is protoporphyrin ix's substrate?
SELECT "Substrate" FROM table_79167 WHERE "Product" = 'protoporphyrin ix'
SELECT "Substrate" FROM "table_79167" WHERE "Product" = 'protoporphyrin ix'