Effects of N,N'-dicyclohexylcarbodiimide and N-(ethoxycarbonyl)-2- ethoxy-1,2-dihydroquinoline on hydride ion transfer and proton translocation activities of mitochondrial nicotinamidenucleotide transhydrogenase
N,N'-Dicyclohexylcarbodiimide (DCCD) inhibits the mitochondrial energy-linked nicotinamidenucleotide transhydrogenase (TH). Recent studies suggested that the inhibition site of DCCD is near the NAD(H) binding site, because NAD(H) and competitive inhibitors protected TH against inhibition by DCCD and, unlike the unmodified TH, the DCCD-modified TH did not bind to NAD- agarose. Others could not demonstrate protection by NADH, obtained data indicating DCCD inhibits proton translocation by TH much more than hydride ion transfer from NADPH to 3-acetylpyridine adenine dinucleotide (AcPyAD), and concluded that DCCD modifies an essential residue in the proton channel of TH. The present studies show that N-(ethoxycarbonyl)-2- ethoxy-1,2-dihydroquinoline (EEDQ) also inhibits TH. The inhibition is pseudo first order at several EEDQ concentrations, and the reaction order with respect to (EEDQ) is unity, suggesting that inhibition involves the interaction of one molecule of EEDQ with one active unit of TH. The EEDQ-modified TH reacts covalently with (/sup 3/H)aniline, suggesting that the residue modified by EEDQ is a carboxyl group. More significantly, it has been shown that the absorbance change of oxonol VI at 630 minus 603 nm is a reliable reporter of TH-induced membrane potential formation in submitochondrial particles and that TH-catalyzed hydride ion transfer from NADPH to AcPyAD and the membrane potential induced by this reaction are inhibited in parallel by either DCCD or EEDQ.
- Research Organization:
- Scripps Clinic and Research Foundation, La Jolla, CA
- OSTI ID:
- 5411127
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 23:26; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AMINES
ANILINE
AROMATICS
AZAARENES
AZINES
BARYONS
BIOLOGICAL EFFECTS
CELL CONSTITUENTS
CHEMICAL BONDS
COENZYMES
COMPARATIVE EVALUATIONS
ELEMENTARY PARTICLES
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
FERMIONS
HADRONS
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROGENASES
IMIDES
IN VITRO
ION EXCHANGE
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MITOCHONDRIA
NAD
NADP
NUCLEONS
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOIDS
OXIDOREDUCTASES
PROTONS
PYRIDINES
QUINOLINES
RESIDUES
TRACER TECHNIQUES
TRANSLOCATION
TRITIUM COMPOUNDS