. Biological structure and function; proceedings. Biochemistry; Cytology. NUCLEOTIDES AND MITOCHONDRIAL FUNCTION 231 These results show that added ATP can influence the redox state of intramitochondrial components of hydrogen transfer such as DPX and flavoprotein. It is to be assumed that ATP exerts its influence through back reactions of oxidative phosphorylation. The energy requirement for the DPX reduction in the presence of succinate or glycerolphosphate—so far only postulated on the basis of thermodynamic reasoning—has been directly demonstrated bv these experiments. This phenomenon appea
. Biological structure and function; proceedings. Biochemistry; Cytology. NUCLEOTIDES AND MITOCHONDRIAL FUNCTION 231 These results show that added ATP can influence the redox state of intramitochondrial components of hydrogen transfer such as DPX and flavoprotein. It is to be assumed that ATP exerts its influence through back reactions of oxidative phosphorylation. The energy requirement for the DPX reduction in the presence of succinate or glycerolphosphate—so far only postulated on the basis of thermodynamic reasoning—has been directly demonstrated bv these experiments. This phenomenon appears to 340- 380 myu. DPN reduction capronat Fig. 2. The reducing effect of ATP on mitochondrial pyridine nucleotides in the presence of non-DPN-linked substrates. Double beam spectrophotometer recordings of suspensions of mitochondria, a. Skeletal muscle mitochondria, 2 • 8 mg. protein ml. b. Heart muscle mitochondria, 2-0 mg. protein/nil. Incubated in 0-3 M sucrose, i mM EDTA, 10 triethanolamine-HCl-buffer, pH 72, 25 , air-saturated. apply to all substrates that can transfer hydrogen to the respiratory chain without a participation of DPX, since also with fatty acids DPX can be reduced at the expense of energy supply from . In agreement with this picture no ATP is required for the reduction of DPX with DPX- specific substrates such as pyruvate plus malate. Further work may be mentioned which was aimed at exluding other possible explanations of this ATP effect. Thus the specificity for ATP and the studies on the conditions for the ATP-effect furnished additional evidence that ATP acts in a reversal of oxidative phosphorylation [15]. In particular, the question arises why ATP is required for DPX reduc- tion in isolated skeletal-muscle mitochondria in contrast to mitochondria. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly
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