Keilin, David

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 Fe atoms of the cytochromes undergo oxidation and reduction during respiration, cycling between the ferrous (Fe2+) and ferric (Fe3+) oxidation states. The absorption spectra of the oxidized and reduced forms differ (fig. 14.4). In the 1930s, David Keilin used this property to measure the oxidation-reduction states of cytochromes in living cells. Under anaerobic conditions, the cytochromes rapidly became reduced in the presence of 02, they became oxidized. Certain molecules that inhibited respiration (CO, N3, or CN ) blocked the oxidation other inhibitors (amy-tal, rotenone, and malonate) blocked the reduction. Keilin found that the transfer of electrons from cytochrome c to 02... 

David Keilin isolated (Germany/UK, Nobel Prize, Medicine, 1953,... 

Cytochromes are extremely important components of electron transfer pathways in chloroplasts and mitochondria. They have three absorption bands in the visible region the a, (3, and y bands. (Absorption of light by cytochromes is not involved in photosynthesis.) In 1925 David Keilin described three types of cytochrome based on the spectral position of their... 

The respiratory cytochrome c found in the mitochondria of all eukaryotes is a protein with one heme c (Fig. 1) and 103-113 amino acids in a single polypeptide chain with no disulfide crosslinks. It is small and easily extracted from ruptured mitochondria, in contrast to the other protein components of the respiratory chain, which are larger and generally membrane-bound. For this reason, cytochrome c was the first cytochrome to be studied extensively, and has received the most attention from biochemists. The story of its discovery by MacMunn in 1884, its violent rejection by chemist and editor Hoppe-Seyler, subsequent neglect until rediscovered by David Keilin in 1925, and extensive characterization by Hugo Theorell and his school, is a familiar story which need not be repeated here. Good accounts of this history are to be found in reviews... 

Cytochromes were discovered and their role in oxidation explored by David Keilin (1887-1963) in England in 1925. Most cytochromes contain the protoporphyrin IX unit found in hemoglobin and myoglobin. However, in cytochromes both the fifth and sixth coordination sites are occupied by proteins. In contrast to hemo-... 

Russian-born British biologist David Keilin (1887-1963) discovers cytochrome. 

Thus from the time of their discovery the two coenzymes were considered to be concerned with fundamentally different processes DPN was regarded as the coenzyme of fermentation (in 1918 Otto Meyerhof showed that the same coenzyme was required for lactic acid production in muscle extracts), whereas TPN was considered to be the coenzyme of respiration. It was expected, therefore, that a link would eventually be found between TPNH and the cytochrome system (Fig. 1). David Keilin and E. F. Hartree > had shown... 

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