Keilin, David

(b. Moscow, Russia, 21 March 1887; d. Cambridge, England, 27 February 1963)

biochemistry, parasitology.

Born of polish parents temporarily residing in Moscow, Keilin received his early schooling at home and then attended the Gorski Gymnasium in Warsaw from 1897 to 1904. After graduation he embarked on premedical studies at the University of Liége, but in 1905 he decided to continue his studies at Paris, where he came under the influence of Maurice Caullery, the distinguished parasitologist at the Laboratorie d’Évolution des Êtres Organisés. In this laboratory Keilin began research dealing with the life cycle of the fly Pollenia rudis and published his first paper in 1909, which formed a major part of his doctoral dissertation, presented at the Sorbonne in 1917.

By 1914 Keilin’s observations had become wellknown, and after the outbreak of World War I he was invited to become research assistant in the laboratory of G. H. F. Nuttall, Quick professor of biology at the University of Cambridge. Keilin occupied this post from 1915 to 1920, when he was elected to a Beit fellowship. In 1921 the Quick laboratory was incorporated into the newly established Molteno Institute for parasitology and Keilin accompanied Nuttall in this move. In 1925 Keilin became university lecturer in parasitology and in 1931 he succeeded Nuttall as Quick professor and as director of the Molteno Institute. Keilin retired from these posts in 1952, but continued active work until his death. Among his many honors was the Copley Medal of the Royal Society (1952).

As a parasitologist Keilin became known through his work on the life cycle of parasitic and free-living Diptera. In his entomological papers (he published about seventy up to 1931), he described eleven protists that were placed in new species or new genera. His interest in the adaptation of the dipterous larvae to the parasitic mode of life led him to a closer study of their respiration, which brought him to biochemical studies on respiratory mechanisms. After 1930 his entomological efforts gave way almost entirely to biochemical work. But as editor (1934–1963) of the journal Parasitology, he continued to influence that field.

Keilin’s entry into biochemistry came during the course of studies (1922–1924) on the life cycle of the horse botfly (Gasterophilus intestinalis). In 1924 he observed with the aid of a microspectroscope the presence of a four-banded absorption spectrum in the muscles of this insect and others and also found a similar spectrum in aerobic microorganisms. The observation that the four-banded spectrum disappeared on shaking the cell suspension with air, and reappeared shortly afterward, led Keilin to conclude that he was dealing with an intracellular respiratory pigment that is widely distributed in nature. He named this pigment cytochrome and in his first paper (1925) on this subject he suggested that the three components of cytochrome (a, b, and c) are iron-porphyrin compounds that serve as catalysts of oxidation-reduction processes in respiring cells, being alternately oxidized by oxygen and reduced by the action of enzymes that dehydrogenate metabolites.

This concept of the role of cytochrome provided a synthesis of the conflicting views of T. Thunberg and H. Wieland, working with dehydrogenases, and those of O. H. Warburg, who emphasized the activation of oxygen by an iron-containing oxidase he termed “respiratory enzyme.” During the period 1925–1935 Keilin’s work provided clear experimental evidence in support of his view that cytochrome is the link between the dehydrogenases and an oxidase. In subsequent investigations (1937–1939) he isolated one of the cytochrome components (cytochrome c) and characterized more fully the oxidase system (cytochromes a and a₃).

During the early years of these studies Keilin came upon the work of C. A. MacMunn, who had reported in 1884 the spectroscopic observation of a muscle pigment which had a four-banded spectrum, and to which MacMunn assigned a role in intracellular respiration. Except for a strong criticism in 1890 by Hoppe-Seyler, MacMunn’s work attracted relatively little attention at the time. Keilin’s finding represented more than a rediscovery of MacMunn’s pigment, however, since Keilin firmly established the chemical position of cytochrome and clearly delineated its role as an electron-carrier system in the metabolic process whereby metabolites are oxidized by oxygen.

The recognition that cytochrome is a protein containing an iron-porphyrin unit led Keilin to study the enzymes catalase and peroxidase; between 1934 and 1958 he described a series of important studies on the mechanism of action of these two iron-porphyrin enzymes. He also examined several copper-containing enzymes and in 1938 discovered hemocuprein, a copper protein of red blood corpuscles. Keilin’s investigation of the enzyme carbonic anhydrase (1939–1944) showed that it is a zinc protein and that it is strongly inhibited by sulfanilamide; the latter result served as a basis for the subsequent development of a valuable drug for the treatment of glaucoma. Other enzymes fruitfully studied by Keilin included the flavoproteins glucose oxidase, D-amino acid oxidase, and xanthine oxidase.

The breadth of Keilin’s biological interests manifested itself in many ways. He conducted studies on the comparative biochemistry of hemoglobin, especially in relation to its presence and function in microorganisms and in the root nodules of leguminous plants. He was interested in the problem of anabiosis, that is, the suspended animation of living things after desiccation and freezing (he preferred to call it cryptobiosis), and his Leeuwenhoek lecture to the Royal Society (published in 1959) on the history of the problem gave clear evidence of his thoroughness and perception as a historian of biology . In the latter years of his life, Keilin began to write a history of intracellular respiration, but did not complete the book. His daughter, Joan, prepared the manuscript for the press and added much new material; the book was published in 1966.

Keilin resided in Cambridge from 1915 to the end of his life. During that time, and especially after 1931, he exerted a profound influence on the development of science at the university, notably in the encouragement of younger men to embark on new lines of research. A few days after his death, M. F. Perutz wrote in The Times of London: “J. C. Kendrew and I owe Keilin a tremendous debt, for he was one of the first to see the potentialities of our physical approach to biochemistry.” In 1962 Perutz and Kendrew were awarded the Nobel Prize in chemistry for their work on the X-ray crystallography of proteins.

BIBLIOGRAPHY

I. Original Works, Keilin’s only book was The History of Cell Respiration and Cytochrome (Cambridge, 1966). He published about 200 scientific articles; a list of his publications follows the article by T. Mann in Biographical Memoirs (see below).

II. Secondary Literature. See the obituary articles by M. Dixon and P. Tate, in Journal of General Microbiology,45 (1966), 159–185; E. F. Hartree, in Biochemical Journal, 89 (1963), 1-5; T. Mann, in Biographical Memoirs of Fellows of the Royal Society, 10 (1964), 183–197; and in Nature, 198 (1963), 736–737; and P. Tate, in Parasitology, 55 (1965), 1–28.

Joseph S. Fruton