Keilin

D. Keilin, The ETstory of Cell Kespiration and Cytochrome, University Press, Cambridge, 1966. 

Mitchell, P., 1979. Keilin s re.spiratory chain concept and its chemiosmotic consequences. Science 206 1148-1159. 

Schor-Fumbarov, T., Keilin, Z., and Tel-Or, E., Characterization of cadmium uptake by the water lily Nymphaea aurora, International Journal of Phytoremediation, 5 (2), 169-179, 2003. 

The third class of haemoproteins, with hexa-coordinate low-spin iron, are the cytochromes. First discovered by McMunn in 1884, they were rediscovered in 1925 by David Keilin. Using a hand spectroscope he observed the characteristic absorption (Soret) bands of the three cytochromes a, b and c in respiring yeast cells, which disappeared upon oxygenation. 

The link between the dehydrogenation of tricarboxylic acid cycle substrates and oxygen uptake was clarified by Keilin between 1925 and... 

Cytochrome c can easily be extracted from tissue particles by dilute salt solutions. It was isolated by Keilin and Hartree in 1930 and shown to contain a porphyrin ring structure. In 1933 Zeilen and Reuter established that cytochrome c was a heme (iron-porphyrin) protein. Slightly different forms of cytochrome a were distinguished in yeast and bacteria by Keilin in 1934 and the different properties of cytochrome a and a3 by Tamiya et al. in 1937. The identity of cytochrome 03, the enzyme which activates oxygen with Warburg s atmungsferment, was proposed by Keilin in 1939. Cytochrome a/a3 was renamed cytochrome oxidase by Malcolm Dixon (1939). The oxidation route then offered was ... 

By 1949 low temperature spectroscopy had been introduced. With this technique Keilin and Hartree detected a further component in the electron transfer chain which had a sharp band at 552 nm. They later showed it to be identical with cytochrome cj, which had first been observed by Yakushiji and Okunuki (1940) during succinate oxidation by cyanide-inhibited beef heart muscle. As the oxidation of cytochrome C was accelerated by cytochrome c, Okunuki and Yakushiji (1941) had placed C] in the chain in the order... 

This was confirmed by Keilin and Hartree using antimycin A as an inhibitor. The antibiotic blocked the reduction of cytochrome cx by NADH or succinate but did not block the reduction of cytochrome b. This site-specific inhibition brought antimycin A into popular use by biochemists in the analysis of electron transfer and oxidative phosphorylation. 

By 1950, Hogeboom and Schneider had prepared relatively pure mitochondria (Chapter 9) which could be used as the oxidizing system rather than crude particulate preparations like the heart muscle system of Keilin and Hartree. The problem still remained for the extraction and identification of the components from the (inner) mitochondrial membrane without denaturation. 

Keilin, D. (1925). On cytochrome, a respiratory pigment common to animals, yeasts and higher Plants. Proc. Roy. Soc. B 98, 312-329. 

Hevesy first used a radioisotope as a tracer. Warburg. Importance of iron pigments in oxidation. Keilin rediscovered cytochromes. Sumner crystallized urease. The Eggletons and Fiske and SubbaRow isolated phospho-creatine. 

The donor types D3, D4, and D6 of Keilin and Nicholls (37) all reduce compound I of Type A enzymes directly to the ferric state in a two-electron process without detectable intermediates. Each of these donors is probably also able to bind in the heme pocket of the free enzyme. Alcohols (type D3) form complexes with free ferric Type A enzymes whose apparent affinities parallel the effectiveness of the same alcohols as compound I donors (39). Formate (type D3) reacts with mammalian ferric enzyme at a rate identical to the rate with which it reduces compound I to free enz5mie (22). Its oxidation by compound I may thus share an initial step analogous to its complex formation with ferric enzyme. Formate also catalyzes the reduction of compound II to ferric enzyme by endogenous donors in the enz5mie (40, 41). Both compound I and compound II may thus share with the free enzyme the ability to ligate formate in the heme pocket. Nitrite, which is oxidized to nitrate by a two-electron reaction with compoimd I (type D4), also forms a characteristic complex with free enzyme (42). In both cases the reaction involves the donor in its protonated (HNO2) form. 

The donor types D2, D4, and D5 of Keilin and Nicholls (37) all reduce compound II to ferric enz5mie in a one-electron process without detectable intermediates. Donors of type D2, phenols and amines, also reduce compound I to compoimd II. Nitrite, the only member of category D4, reduces compoimd I in a two-electron step as described earlier. Donors of type D1 reduce compound I to compound II, but have no appreciable effect upon compound II itself Reactivity of the one-electron donors seems independent of heme pocket binding in the free enzyme. 

Sauder, Wallitt, Rissmann and Keilin, Tyco Labs., Proc. 

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