CREATE TABLE table_79168 ("Enzyme" TEXT, "Location" TEXT, "Substrate" TEXT, "Product" TEXT, "Chromosome" TEXT, "OMIM" FLOAT, "Porphyria" TEXT)

Which substrate has an OMIM of 176000?
SELECT "Substrate" FROM table_79168 WHERE "OMIM" = '176000'
SELECT "Substrate" FROM "table_79168" WHERE "OMIM" = '176000'