2-Heptyl-4-hydroxyquinoline

In H. salinarium (cutinibnim), NADH is oxidized through c-type cytochromes and an cytochrome a oxidase. 2-heptyl-4-hydroxyquinoline-yV-oxide (HOQNO) inhibits electron transport chain at the level of the NADH dehydrogenase. The salt dependence of the NADH oxidase system indicates that the salt dependence of the NADH oxidase system is a reflection of the sensitivity of the NAD dehydrogenase [95]. 

The biosynthesis of 2-alkyl- and 2-arylquinoline alkaloids was investigated by Luckner and co-workers. For example, anthranilic acid was incorporated intact into 2-heptyl-4-hydroxyquinoline 339 in the microorganism Pseudomonas aeruginosa. Acetate and malonate are also precursors, and degradation experiments showed that the side chain was... 

In the case of S. japonica, the A is eduline, formed directly from a in the decarboxylation process. In the case of microorganisms, for example Pseudomonas aeruginosa, the a is incorporated directly to the A, which is 2-heptyl-4-hydroxyquinoline. 

Heptyl-4- hydroxyquinoline 2-n-C7Hi5,4-OH Alteromonas sp.(marine bacterium), [41], Pseudomonas aeruginosa [41]... 

Abbreviations AA, antimycin BAL, British Anti-Lewisite (2,3-dimercaptopropanol) DCCD, dicyclo-hexylcarbodiimide DTNB, 5,5 -dithiobis(2-nitrobenzoate) oxidoreduction potential relative to the Normal Hydrogen Electrode midpoint oxidoreduction potential E midpoint oxidoreduction potential at pH = x FeS, iron-sulphur (centre or protein) FMN, flavin mononucleotide HMHQQ, 7-( n-heptadecyl)mercapto-6-hydroxy-5,8-quinolinequinone HOQNO, 2-/i-heptyl-4-hydroxyquinoline N-oxide Lb, leghaemoglobin MX, myxothiazol NEM, 7V-ethylmaIeimide pmf, protonmotive force, electrochemical proton gradient Q, ubiquinone Qj i, ubiquinone bound to Complex I SQ, ubise-miquinone SQ , ubisemiquinone anion UHDBT, 5- -undecyl-6-hydroxy-4,7-dioxobenzothiazol. 

FIGURE 3. Summary of loci of inhibitor-resistant mutants in yeast (20,21) and mouse (22) mitochondrial cyt b. an, antimycin A du, DCMU hq, n-heptyl-4-hydroxyquinoline-N-oxide, HQNO my, myxathiazol mu, mucidin st, stigmatellin. 

The addition of fumarate to the suspension of P. freudenreichii oxidizing lactate was shown to result in a partial oxidation of cytochromes b and 02 (de Vries et al., 1977). In the presence of 2H-heptyl-4-hydroxyquinoline-N-oxide, an inhibitor of cytochrome b, lactate dehydrogenase activity was reduced by 85% if fumarate served as an electron acceptor, but only by 25% in the presence of methylene blue (in the latter case H2 is transferred to the dye without participation of cytochrome b). Keeping in mind the evidence presented above, the propionic acid fermentation can be viewed as a harmonious combination of the soluble and membrane-bound redox enzymes. The involvement of cytochrome b in anaerobic electron transport to fiimarate confirms the suggestion (Bauchop and Elsden, 1960) that there is an oxidative phosphorylation site between fumarate and succinate in propionibacteria. 

The rate of cycling cind the redox poise of components in the steady state was dependent on the relative amounts of quinone and cytochrome c (plastocyanin) added and on the number of electrons present in the system. The pH was also critical a pH too high caused significant non-enzymatic electron transfers whereas a pH too low decreased be complex activities. Optimal pH values were around 7.2 for RCbc vesicles and around 6.5 for PSbf vesicles. Under appropriate conditions, redox changes of cytochrome b could also be observed. Antimycin A inhibited cytochrome b reoxidation and myxothiazol inhibited donation into the be complex in the RCbc system, but both were without effect of the PSbf system. Instead 2-n-heptyl-4-hydroxyquinoline-N-oxide could be used to inhibit cytochrome b reoxidation and DNP-INT could be used to inhibit donation into the bf complex. Figure 1 illustrates some typical results. 

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