Article (Scientific journals)
Product inhibition of mammalian thiamine pyrophosphokinase is an important mechanism for maintaining thiamine diphosphate homeostasis
Sambon, Margaux; Pavlova, Oleksandra; Alhama-Riba, Judit et al.
2022In Biochimica et Biophysica Acta - General Subjects, 1866 (3), p. 130071
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Keywords :
Thiamine diphosphate; Thiamine deficiency; Thiamine supplementation
Abstract :
[en] Background: Thiamine diphosphate (ThDP), an indispensable cofactor for oxidative energy metabolism, is syn- thesized through the reaction thiamine + ATP ⇆ ThDP + AMP, catalyzed by thiamine pyrophosphokinase 1 (TPK1), a cytosolic dimeric enzyme. It was claimed that the equilibrium of the reaction is in favor of the for- mation of thiamine and ATP, at odds with thermodynamic calculations. Here we show that this discrepancy is due to feedback inhibition by the product ThDP. Methods: We used a purified recombinant mouse TPK1 to study reaction kinetics in the forward (physiological) and for the first time also in the reverse direction. Results: Keq values reported previously are strongly underestimated, due to the fact the reaction in the forward direction rapidly slows down and reaches a pseudo-equilibrium as ThDP accumulates. We found that ThDP is a potent non-competitive inhibitor (Ki ≈ 0.4 μM) of the forward reaction. In the reverse direction, a true equi- librium is reached with a Keq of about 2 × 10− 5, strongly in favor of ThDP formation. In the reverse direction, we found a very low Km for ThDP (0.05 μM), in agreement with a tight binding of ThDP to the enzyme. General significance: Inhibition of TPK1 by ThDP explains why intracellular ThDP levels remain low after administration of even very high doses of thiamine. Understanding the consequences of this feedback inhibition is essential for developing reliable methods for measuring TPK activity in tissue extracts and for optimizing the therapeutic use of thiamine and its prodrugs with higher bioavailability under pathological conditions.
Research center :
Giga-Neurosciences - ULiège
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
Sambon, Margaux
Pavlova, Oleksandra
Alhama-Riba, Judit
Wins, Pierre
Brans, Alain  ;  Université de Liège - ULiège > Département des sciences de la vie > Centre d'ingénierie des protéines
Bettendorff, Lucien  ;  Université de Liège - ULiège > GIGA Neurosciences - Neurophysiology
Language :
English
Title :
Product inhibition of mammalian thiamine pyrophosphokinase is an important mechanism for maintaining thiamine diphosphate homeostasis
Publication date :
2022
Journal title :
Biochimica et Biophysica Acta - General Subjects
ISSN :
0304-4165
eISSN :
1872-8006
Publisher :
Elsevier, Netherlands
Volume :
1866
Issue :
3
Pages :
130071
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
FRIA - Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture [BE]
Erasmus+ [BE]
Fonds Léon Fredericq [BE]
Funding text :
Experimental Scholarship for Central & Eastern Europe from the FEBS
Available on ORBi :
since 24 December 2021

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