title: The oxygen-independent coproporphyrinogen III oxidase HemN utilizes harderoporphyrinogen as a reaction intermediate during conversion of coproporphyrinogen III to protoporphyrinogen IX.
abstract: During heme biosynthesis the oxygen-independent coproporphyrinogen III oxidase HemN catalyzes the oxidative decarboxylation of the two propionate side chains on rings A and B of coproporphyrinogen III to the corresponding vinyl groups to yield protoporphyrinogen IX. Here, the sequence of the two decarboxylation steps during HemN catalysis was investigated. A reaction intermediate of HemN activity was isolated by HPLC analysis and identified as monovinyltripropionic acid porphyrin by mass spectrometry. This monovinylic reaction intermediate exhibited identical chromatographic behavior during HPLC analysis as harderoporphyrin (3-vinyl-8,13,17-tripropionic acid-2,7,12,18-tetramethylporphyrin). Furthermore, HemN was able to utilize chemically synthesized harderoporphyrinogen as substrate and converted it to protoporphyrinogen IX. These results suggest that during HemN catalysis the propionate side chain of ring A of coproporphyrinogen III is decarboxylated prior to that of ring B.
authors.affiliation: Division of Structural Biology, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Rand
authors.forename: Claudia
authors.initials: C
authors.lastname: Noll
authors.forename: Hans Martin
authors.initials: HM
authors.lastname: Schiebel
authors.forename: Dorit
authors.initials: D
authors.lastname: Kemken
authors.forename: Thomas
authors.initials: T
authors.lastname: Dülcks
authors.forename: Markus
authors.initials: M
authors.lastname: Kalesse
authors.forename: Dirk W
authors.initials: DW
authors.lastname: Heinz
authors.forename: Gunhild
authors.initials: G
authors.lastname: Layer
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003304:Coproporphyrinogen Oxidase / Q000378:metabolism*; D003305:Coproporphyrinogens / Q000378:metabolism*; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D011165:Porphyrinogens / Q000378:metabolism*; D011524:Protoporphyrins / Q000096:biosynthesis*
chemical_list: D003305:Coproporphyrinogens; D011165:Porphyrinogens; D011524:Protoporphyrins; C028026:coproporphyrinogen III; C018563:harderoporphyrinogen; C011539:protoporphyrinogen; D003304:Coproporphyrinogen Oxidase