title: Dihydroorotate dehydrogenase is a high affinity binding protein for A77 1726 and mediator of a range of biological effects of the immunomodulatory compound.
abstract: A protein with high affinity (Kd 12 nM) for the immunomodulatory compound A77 1726 has been isolated from mouse spleen and identified as the mitochondrial enzyme dihydroorotate dehydrogenase (EC 1.3.3.1). The purified protein had a pI 9.6-9.8 and a subunit Mr of 43,000. Peptides derived from the mouse protein displayed high microsequence similarity to human and rat dihydroorotate dehydrogenase with, respectively, 35 and 39 out of 43 identified amino acids identical. Dihydroorotate dehydrogenase catalyzes the fourth step in de novo pyrimidine biosynthesis. The in vitro antiproliferative effects of A77 1726 are mediated by enzyme inhibition and can be overcome by addition of exogenous uridine. The rank order of potency of A77 1726 and its analogues in binding or enzyme inhibition was similar to that for inhibition of the mouse delayed type hypersensitivity response. It is proposed that inhibition of dihydroorotate dehydrogenase is an in vivo mechanism of action of the A77 1726 class of compounds. This was confirmed using uridine to counteract inhibition of the murine acute graft versus host response.
authors.affiliation: Immunology Domain, Hoechst Roussel, Covingham, Swindon, United Kingdom.
authors.forename: R A
authors.initials: RA
authors.lastname: Williamson
authors.forename: C M
authors.initials: CM
authors.lastname: Yea
authors.forename: P A
authors.initials: PA
authors.lastname: Robson
authors.forename: A P
authors.initials: AP
authors.lastname: Curnock
authors.forename: S
authors.initials: S
authors.lastname: Gadher
authors.forename: A B
authors.initials: AB
authors.lastname: Hambleton
authors.forename: K
authors.initials: K
authors.lastname: Woodward
authors.forename: J M
authors.initials: JM
authors.lastname: Bruneau
authors.forename: P
authors.initials: P
authors.lastname: Hambleton
authors.forename: D
authors.initials: D
authors.lastname: Moss
authors.forename: T A
authors.initials: TA
authors.lastname: Thomson
authors.forename: S
authors.initials: S
authors.lastname: Spinella-Jaegle
authors.forename: P
authors.initials: P
authors.lastname: Morand
authors.forename: O
authors.initials: O
authors.lastname: Courtin
authors.forename: C
authors.initials: C
authors.lastname: Sautés
authors.forename: R
authors.initials: R
authors.lastname: Westwood
authors.forename: T
authors.initials: T
authors.lastname: Hercend
authors.forename: E A
authors.initials: EA
authors.lastname: Kuo
authors.forename: E
authors.initials: E
authors.lastname: Ruuth
mesh_terms: D000595:Amino Acid Sequence; D000814:Aniline Compounds / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D002455:Cell Division / Q000187:drug effects; D003437:Crotonates; D000090722:Dihydroorotate Dehydrogenase; D006131:Growth Inhibitors / Q000737:chemistry; D006885:Hydroxybutyrates / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009570:Nitriles; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D013154:Spleen / Q000378:metabolism; D014052:Toluidines; D014529:Uridine / Q000494:pharmacology
chemical_list: D000814:Aniline Compounds; D003437:Crotonates; D000090722:Dihydroorotate Dehydrogenase; D006131:Growth Inhibitors; D006885:Hydroxybutyrates; D009570:Nitriles; D014052:Toluidines; C527525:teriflunomide; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D014529:Uridine