SITES OF INHIBITION OF MITOCHONDRIAL ELECTRON-TRANSPORT BY D1, AN ORGANIC-SOLVENT EXTRACTABLE COMPONENT FROM BURN ESCHAR

The inhibitory sites of component D1, isolated by extracting burn esch ar with ethyl acetate, on rat liver mitochondrial respiratory chain wa s investigated. By using changes of the redox state of NADPH in variou s respiratory states, the effect of D1 on electron flow through the ph osphorylation site 1 was studied. It was found that D1 did not interfe re with electron transport through site 1, nor did it inhibit the acti vity of NADH: duroquinone reductase. The functional state of site 2 wa s tested directly by using duroquinol as an artificial electron donor and cytochrome c as electron acceptor. D1 inhibited the activity of th is enzyme in a dose-dependent manner. The redox state of the electron carrier cytochrome b was not influenced by D1. However, a transient pr ocess of oxidation of cytochrome c, was demonstrated, suggesting a bri ef inhibitory process in the reducing side of it. Two inhibitory sites in site 2 were found by studying the TMPD and DCIP bypasses. One was at the reducing side of cytochrome c1, and the other was at the reduci ng side of cytochrome b. Further studies are needed to find out the ex act position and nature of these inhibitory sites.