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18 April 2019 Purification of Adult Hymenolepis diminuta (CESTODA) Mitochondrial NADPH→NAD+ Transhydrogenase
Qui Fu, Ronald Ma, Carmen F. Fioravanti
Author Affiliations +
Abstract

The mitochondrial, inner-membrane–associated, reversible NADPH→NAD+ transhydrogenase of the energetically anaerobic adult cestode Hymenolepis diminuta connects NADPH generation, via a mitochondrial NADP+-specific “malic” enzyme, with NADH formation needed for electron transport. In reducing the pyridine nucleotide, the enzyme concomitantly catalyzes transmembrane proton translocation, thereby coupling NADH formation to ATP generation or NADPH formation to ATP hydrolysis. Detergent-solubilized transhydrogenase, from isolated mitochondrial membranes, was purified to apparent homogeneity using ion exchange and hydroxylapatite chromatographies. The enzyme displayed a monomeric Mr of ∼110 kDa and required phospholipid, without which activity was rapidly lost. Of the phospholipids examined, phosphatidylcholine was the most effective. Transhydrogenase-catalyzed NADH formation was inhibited by NAD(P)+ and adenylates, suggesting regulatory effects of the pyridine nucleotides and effects of pyridine nucleotide-simulating molecules. In keeping with its proton-translocating function, the enzyme was inhibited by dicyclohexylcarbodiimide. The isolated enzyme catalyzed neither NADH→NADP+ nor NADH→NAD+ transhydrogenations, thereby suggesting a need for a minimal coupling to electron transport for the NADH→NADP+ reaction as well as enzyme specificity. Anti-transhydrogenase monospecific antibodies proved inhibitory to NADPH→NAD + transhydrogenation catalyzed by both isolated and membrane-associated enzymes. This purification study apparently represents a first for parasitic helminths or multicellular invertebrates generally and establishes a framework for evaluating the transhydrogenase as a potential site for specific chemotherapeutic attack.

© American Society of Parasitologists 2019
Qui Fu, Ronald Ma, and Carmen F. Fioravanti "Purification of Adult Hymenolepis diminuta (CESTODA) Mitochondrial NADPH→NAD+ Transhydrogenase," Journal of Parasitology 105(2), 321-329, (18 April 2019). https://doi.org/10.1645/18-55
Published: 18 April 2019
KEYWORDS
Adenylates
Antibody Generation
Cestode
DCCD
enzyme purification
Hymenolepis diminuta
inhibition
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