PubMed Health⌕ Search

Biomedical subjects

H Beinert

Publications and source records attributed to H Beinert.

At least 145 records · Page 8Linked to original sources
PubMed1970

Reaction sites of rotenone, piericidin A, and amytal in relation to the nonheme iron components of NADH dehydrogenase.

The locus of inhibition of nicotinamide adenine dinucleotide, reduced form (NADH) oxidation in mitochondria by rotenone, piercidin A, and barbiturates is considered in the light of available information. Most lines of evidence indicate that the point of inhibition is on the O(2) side of NADH dehydrogenase. Kinetic experiments on the substrate-induced appearance of the electron paramagnetic resonance signal at g = 1.94 in membrane preparations (ETP) reveal that these inhibitors do not interfere with the reduction of the electron paramagnetic resonance detectable iron by NADH. Our spectrophotometric studies on complex I give no evidence for absorbance differences between untreated and rotenone or piericidin inhibited preparations, which can be attributed to nonheme iron. Whatever changes were observed appear to be due to cytochromes. These experiments, therefore, do not support the idea that in inhibited preparations electron transport is interrupted between the flavin and nonheme iron components of NADH dehydrogenase. The specific binding of rotenone and piericidin seems to involve both lipid and protein. The possibility that NADH dehydrogenase participates in the binding is suggested by the apparent stoichiometric relation between specific binding site titer and NADH dehydrogenase content and the profound effect of mersalyl inhibition of the enzyme on piericidin binding capacity.ETP, electron transport particle.

Amobarbital↗
PubMed1970

Spin-state changes in cytochrome P-450cam on binding of specific substrates.

The electron paramagnetic resonance signals of the soluble P-450 cytochrome from Pseudomonas putida were observed at temperatures from 4.2 to 80 degrees K. As isolated, P-450 has a signal typical of a low spin ferric-heme compound with sulfur as one of the axial ligands (g = 2.45, 2.26, 1.91(5)). We also detected a minor signal typical of high spin ferric heme (g = 8, 4, 1.8) equivalent to less than 7% of the heme at temperatures below 20 degrees K. On titration with the substrate, (+)-camphor, the low spin signal decreased and the high spin signal increased, maximally representing about 60% of the heme. For reasons not thus far understood, 40% of the heme is not converted to high spin by either (+) or (-)-camphor. The high spin signal has a rhombic character which is stronger than any previously observed with a heme compound (E = 0.33 cm(-1); D = 3.8 cm(-1); E/D = 0.087). We conclude that P-450(cam) as isolated is equal to or more than 95% in a low spin form probably having sulfur as one of the axial ligands. The binding of substrate displaces this ligand sufficiently to allow for conversion from a low to a high spin form.

Cold Temperature↗