title: Kinetic studies of novel di- and tri-propionate substrates for the chicken red blood cell enzyme coproporphyrinogen oxidase.
abstract: Coproporphyrinogen oxidase is an important enzyme in heme biosynthesis and catalyses the sequential oxidative decarboxylation of propionates on the A and B rings of the porphyrinogen ring. The effects of substituents on the C and D rings have not been systematically evaluated for their effects on the kinetic constants, K(m) and V(max). A series of synthetic porphyrinogens have been tested for their ability to affect these kinetic constants for the chicken enzyme. The enzyme exhibited the largest V(max) when incubated with the authentic substrate and was clearly able to distinguish between various substituents on the C and D rings of the macrocycle. When co-incubated with substrate, the authentic product, protoporphyrinogen-IX, appears to inhibit coproporphyrinogen oxidase and this may have an important role in the regulation of this enzyme. Thus the model for the active site of this enzyme should be modified to take these factors into account.
authors.affiliation: Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA. mjones@xenon.che.ilstu.edu
authors.forename: M A
authors.initials: MA
authors.lastname: Jones
authors.forename: J
authors.initials: J
authors.lastname: He
authors.forename: T D
authors.initials: TD
authors.lastname: Lash
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002645:Chickens; D003304:Coproporphyrinogen Oxidase / Q000378:metabolism*; D003305:Coproporphyrinogens / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology*; D006418:Heme / Q000096:biosynthesis*; D007700:Kinetics; D008958:Models, Molecular; D011165:Porphyrinogens / Q000138:chemical synthesis / Q000378:metabolism*; D011422:Propionates / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D003305:Coproporphyrinogens; D011165:Porphyrinogens; D011422:Propionates; C028026:coproporphyrinogen III; D006418:Heme; D003304:Coproporphyrinogen Oxidase