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Biomedical subjects

M E Koller

Publications and source records attributed to M E Koller.

42 records · Page 3Linked to original sources
PubMed1976

Studies on the ferrochelatase activity of isolated rat liver mitochondria with special reference to the effect of oxidizable substrates and oxygen concentration.

The mitochondrial ferrochelatase activity has been studied in coupled rat liver mitochondria using deuteroporphyrin IX (incorporated into liposomes of lecithin) and Fe(III) or Co(II) as the substrates. 1. It was found that respiring mitochondria catalyze the insertion of Fe(II) and Co(II) into deuteroporphyrin. When Fe(III) was used as the metal donor, the reaction revealed an absolute requirement for a supply of reducing equivalents supported by the respiratory chain. 2. A close correlation was found between the disappearance of porphyrin and the formation of heme which allows an accurate estimate of the extinction coefficient for the porphyrin to heme conversion. The value deltae (mM-1 - cm-1) = 3.5 for the wavelength pair 498 509 nm, is considerably lower than previously reported. 3. The maximal rate of deuteroheme synthesis was found to be approx. 1 nM - min-1 - mg-1 of protein at 37 degrees C, PH 7.4 and optimal substrate concentrations, i.e. 75 muM Fe(III) and 50 muM deuteroporphyrin. 4. Provided the mitochondria are supplemented with an oxidizable substrate, the presence of oxygen has no effect on the rate of deuteroheme synthesis.

Animals↗
PubMed1976

Transferrin and iron uptake by isolated rat liver mitochondria.

Isolated rat liver mitochondria accumulate iron from the suspending medium when [59Fe]transferrin is used as a model compound. The accumulation proceeds by two different mechanisms, i.e. by an energy-independent and an energy-dependent (uncoupler sensitive) mechanism, which have different time, pH, and temperature dependencies. The energy-dependent accumulation, which is inhibited by ruthenium red and sulphydryl reagents, reaches a saturation level of approx. 30 pmoles iron/mg protein during 30 min incubation. The energy-independent accumulation of iron-transferrin reveals no saturation kinetics, it is inhibited neither by ruthenium red nor by N-ethylmaleimide, and it proceeds linearly for at least 90 min. With [125I]transferrin as a model compound, quantitatively the energy-independent accumulation is as reported for [59Fe]transferrin. There is, however, no energy-dependent accumulation of [125I]transferrin. The results indicate that the energy-dependent accumulation of [59Fe]transferrin represents a process by which mitochondria accumulate iron from transferrin.

Animals↗