PMID- 10658902
OWN - NLM
STAT- MEDLINE
DCOM- 20000224
LR  - 20190826
IS  - 0009-2797 (Print)
IS  - 0009-2797 (Linking)
VI  - 124
IP  - 1
DP  - 2000 Jan 3
TI  - Kinetics of inhibition of human and rat dihydroorotate dehydrogenase by
      atovaquone, lawsone derivatives, brequinar sodium and polyporic acid.
PG  - 61-76
AB  - Mitochondrially-bound dihydroorotate dehydrogenase (EC 1.3.99.11) catalyzes the
      fourth sequential step in the de novo synthesis of uridine monophosphate. The
      enzyme has been identified as or surmised to be the pharmacological target for
      isoxazol, triazine, cinchoninic acid and (naphtho)quinone derivatives, which
      exerted antiproliferative, immunosuppressive, and antiparasitic effects. Despite 
      this broad spectrum of biological and clinical relevance, there have been no
      comparative studies on drug-dihydroorotate dehydrogenase interactions. Here, we
      describe a study of the inhibition of the purified recombinant human and rat
      dihydroorotate dehydrogenase by ten compounds. 1,4-Naphthoquinone,
      5,8-hydroxy-naphthoquinone and the natural compounds juglon, plumbagin and
      polyporic acid (quinone derivative) were found to function as alternative
      electron acceptors with 10-30% of control enzyme activity. The human and rat
      enzyme activity was decreased by 50% by the natural compound lawsone ( > 500 and 
      49 microM, respectively) and by the derivatives dichloroally-lawsone (67 and 10
      nM), lapachol (618 and 61 nM) and atovaquone (15 microM and 698 nM). With respect
      to the quinone co-substrate of the dihydroorotate dehydrogenase, atovaquone (Kic 
      = 2.7 microM) and dichloroally-lawsone (Kic = 9.8 nM) were shown to be
      competitive inhibitors of human dihydroorotate dehydrogenase. Atovaquone (Kic =
      60 nM) was also acompetitive inhibitor of the rat enzyme. Dichloroally]-lawsone
      was found to be a time-dependent inhibitor of the rat enzyme, with the lowest
      inhibition constant (Ki* = 0.77 nM) determined so far for mammalian
      dihydroorotate dehydrogenases. Another inhibitor, brequinar was previously
      reported to be a slow-binding inhibitor of the human dihydroorotate dehydrogenase
      [W. Knecht, M. Loffler, Species-related inhibition of human and rat dihyroorotate
      dehydrogenase by immunosuppressive isoxazol and cinchoninic acid derivatives,
      Biochem. Pharmacol. 56 (1998) 1259-1264]. The slow binding features of this
      potent inhibitor (Ki* = 1.8 nM) with the human enzyme, were verified and seen to 
      be one of the reasons for the narrow therapeutic window (efficacy versus
      toxicity) reported from clinical trials on its antiproliferative and
      immunosuppressive action. With respect to the substrate dihydroorotate,
      atovaquone was an uncompetitive inhibitor of human dihydroorotate dehydrogenase
      (Kiu = 11.6 microM) and a non-competitive inhibitor of the rat enzyme (Kiu = 905/
      Kic = 1,012 nM). 1.5 mM polyporic acid, a natural quinone from fungi, influenced 
      the activity of the human enzyme only slightly; the activity of the rat enzyme
      was decreased by 30%.
FAU - Knecht, W
AU  - Knecht W
AD  - School of Medicine, Institute for Physiological Chemistry, Phillipps University
      Marburg, Germany.
FAU - Henseling, J
AU  - Henseling J
FAU - Loffler, M
AU  - Loffler M
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Ireland
TA  - Chem Biol Interact
JT  - Chemico-biological interactions
JID - 0227276
RN  - 0 (Benzoquinones)
RN  - 0 (Biphenyl Compounds)
RN  - 0 (Enzyme Inhibitors)
RN  - 0 (Naphthoquinones)
RN  - 0 (Quinones)
RN  - 0 (polyporic acid)
RN  - 5XL19F49H6 (brequinar)
RN  - EC 1.- (Oxidoreductases)
RN  - EC 1.3.- (Oxidoreductases Acting on CH-CH Group Donors)
RN  - EC 1.3.5.2 (dihydroorotate dehydrogenase)
RN  - TLH4A6LV1W (lawsone)
RN  - Y883P1Z2LT (Atovaquone)
SB  - IM
MH  - Animals
MH  - Atovaquone
MH  - Benzoquinones/metabolism/pharmacology
MH  - Binding, Competitive
MH  - Biphenyl Compounds/metabolism/pharmacology
MH  - Enzyme Inhibitors/metabolism/*pharmacology
MH  - Humans
MH  - Inhibitory Concentration 50
MH  - Kinetics
MH  - Naphthoquinones/metabolism/pharmacology
MH  - Oxidoreductases/*antagonists & inhibitors/metabolism
MH  - *Oxidoreductases Acting on CH-CH Group Donors
MH  - Quinones/metabolism/pharmacology
MH  - Rats
MH  - Substrate Specificity
EDAT- 2000/02/05 09:00
MHDA- 2000/02/26 09:00
CRDT- 2000/02/05 09:00
PHST- 2000/02/05 09:00 [pubmed]
PHST- 2000/02/26 09:00 [medline]
PHST- 2000/02/05 09:00 [entrez]
AID - S0009-2797(99)00144-1 [pii]
AID - 10.1016/s0009-2797(99)00144-1 [doi]
PST - ppublish
SO  - Chem Biol Interact. 2000 Jan 3;124(1):61-76. doi: 10.1016/s0009-2797(99)00144-1.