This paramagnetic sulfhydryl-modifying reagent (FW = 129.14 g/mol; CAS 15622-62-5; lmax = 460 nm), also known systematically as 4-amino-2,5- dihydro-2-imino-5,5-dimethyl-1H-imidazol-1-yloxy, reacts with many sulfhydryl-containing substances, with loss of its characteristic red color. Porphyrexide is also be used as an oxidant substrate by a number of enzymes, including galactose oxidase. The Escherichia coli sulfite reductase heme protein subunit reacts at nearly unit stoichiometrry with porphyrexide to produce a ferrisiroheme p-cation radical. Target(s): alcohol dehydrogenase; glyceraldehyde-3-phosphate dehydrogenase; a-glycerophosphate dehydrogenase; lactate dehydrogenase; and pyruvate decarboxylase.
