Effect of sulfhydryl modifications on transhydrogenase

Journal Article · Thu May 01 04:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:6956317

Modrak, D; Fisher, R R

The effect of various sulfhydryl modification agents on the NADPH..-->..AcPyAD activity of bovine heart pyridine dinucleotide transhydrogenase in the presence and absence of substrates was investigated. Copper (o-phenanthroline)/sub 2/, (Cu(OP)/sub 2/); 5,5'-dithiobis-(2-nitrobenzoic acid), (DTNB); and N-ethylmaleimide (NEM) were able to completely inhibit the activity of transhydrogenase in the absence of substrates. Inhibition of DTNB and Cu(OP)/sub 2/ was accompanied by a change in mobility on SDS-PAGE of approximately 2000 Daltons. NADP/sup +/ provided protection against Cu(OP)/sub 2/, DTNB and NEM while NADPH protected against Cu(OP)/sub 2/ and DTNB. NAD(H) provided no protection against inactivation. The effects of DTNB and Cu(OP)/sub 2/ were reversible upon addition of dithiothreitol and BETA-mercaptoethanol. It was previously shown by DTNB titration that there were two sulfhydryls exposed on the surface and four buried in the native enzyme. The use of Cu(OP)/sub 2/, DTNB and NEM indicate that one sulfhydryl is contained within the NADP-binding site and the other is peripheral to this site, but not in the NAD-binding site, and that these two sulfhydryls are spatially vicinal.

• Research Organization: Univ. of South Carolina, Columbia
• OSTI ID: 6956317
• Report Number(s): CONF-8606151-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
• Country of Publication: United States
• Language: English

Related Subjects

560300* -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
ANTIMITOTIC DRUGS
AROMATICS
AZAARENES
BENZOIC ACID
BIOLOGICAL EFFECTS
BODY
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CATTLE
COENZYMES
COPPER
DOMESTIC ANIMALS
DRUGS
ELEMENTS
ENZYME ACTIVITY
ENZYMES
HEART
HETEROCYCLIC COMPOUNDS
HYDROGENASES
IMIDES
MAMMALS
METALS
MONOCARBOXYLIC ACIDS
NADP
NEM
NITRO COMPOUNDS
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
OXIDOREDUCTASES
PHENANTHROLINES
RADIOSENSITIZERS
RUMINANTS
THIOLS
TRANSITION ELEMENTS
VERTEBRATES