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Malcolm Dixon (biochemist)

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Malcolm Dixon
FRS
Born18 April 1899
Cambridge, England
Died7 December 1985(1985-12-07) (aged 86)
Cambridge, England
EducationUniversity of Cambridge (BA, MA, PhD)
Known forEnzymes (with Edwin C. Webb)
Scientific career
FieldsBiochemistry
InstitutionsUniversity of Cambridge
ThesisThe types of oxidation-reduction system, enzymic and non-enzymic, present in living animal tissues (1925)
Doctoral advisorFrederick Hopkins
Doctoral students

Malcolm Dixon (18 April 1899 – 7 December 1985) was a British biochemist.

Education and early life

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Dixon was born in Cambridge, England, to Allick Page Dixon and Caroline Dewe Dixon (née Mathews).[2] He was educated at home (having come down with tuberculosis aged 12) and at Emmanuel College, Cambridge, where he graduated with a BA in Natural Sciences in 1921 and was later an 1851 Exhibition Senior Student.)[2][3] He was awarded his PhD at Cambridge in 1925, for research supervised by Frederick Gowland Hopkins.[4]

Research and career

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Dixon's research investigated the purification of enzymes and the enzyme kinetics of enzyme-catalyzed reactions. He studied the oxidation of glutathione and other thiols by molecular oxygen and measured the redox potential of the thiol-disulfide system, also establishing that the oxidation of glutathione was catalyzed by trace metals.[5] He investigated xanthine oxidase,[6] and thereby elucidated many aspects of the chemistry of dehydrogenases. He showed that the hydrogen peroxide formed in the reaction of xanthine oxidase with molecular oxygen inactivated the enzyme and that the inhibition could be relieved by the addition of catalase,[7] thus helping to establish a biochemical role for the latter enzyme. Dixon published a series of papers on D-amino acid oxidase,[8] detailing the kinetics and thermodynamics of association of the coenzyme with the apoprotein, the substrate and inhibitor specificity, and the effect of pH on the kinetic constants.

Dixon was an expert on the theory and use of manometers.[9] In 1931, he collaborated with David Keilin and Robin Hill to determine the first absorption spectrum of a cytochrome, cytochrome c.[10] Dixon studied the chemistry of lachrymators and mustard gas and proposed a phosphokinase theory to explain their mode of action.[11]

Dixon proposed a widely used way of plotting enzyme inhibition data, commonly known as the Dixon plot, in which reciprocal rate is plotted against the inhibitor concentration.[12] Rather confusingly, the same name is sometimes given to a quite different plot proposed by Dixon in the same year for analysing pH dependences, in which the logarithm of a Michaelis–Menten parameter is plotted against pH.[13]

Enzymes (Dixon & Webb)

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Dixon's classic book Enzymes, written with Edwin C. Webb and published in 1958,[14] with further editions in 1964[15] and 1979,[16] had a great influence of the development of biochemistry. It contained one of the first major efforts to devise a systematic way of classifying and naming enzymes. This formed the starting point for the present classification by the IUBMB.[17]

Awards and honours

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Dixon was elected a Fellow of the Royal Society (FRS) in 1942[2] and became a Fellow of King's College, Cambridge in 1950. He died in Cambridge in 1985.

References

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  1. ^ a b c d "Chemistry Tree".
  2. ^ a b c Perham, R. N. (1988). "Malcolm Dixon. 18 April 1899-7 December 1985". Biographical Memoirs of Fellows of the Royal Society. 34: 98–131. doi:10.1098/rsbm.1988.0005. ISSN 0080-4606. PMID 11616120.
  3. ^ "DIXON, Malcolm". Who's Who & Who Was Who. Vol. 2024 (online ed.). A & C Black. (Subscription or UK public library membership required.)
  4. ^ Dixon, Malcolm (1925). The types of oxidation-reduction system, enzymic and non-enzymic, present in living animal tissues (PhD thesis). University of Cambridge.
  5. ^ Dixon, Malcolm; Tunnicliffe, Hubert Erlin (1927). "On the Reducing Power of Glutathione and Cysteine". Biochemical Journal. 21 (4): 844–851. doi:10.1042/bj0210844. PMC 1251992. PMID 16743909.
  6. ^ Dixon, M.; Keilin, D. (1936). "The action of cyanide and other respiratory inhibitors on xanthine oxidase". Proceedings of the Royal Society of London. Series B, Biological Sciences. 119 (813): 159–190. Bibcode:1936RSPSB.119..159D. doi:10.1098/rspb.1936.0004.
  7. ^ Dixon, Malcolm (1925). "Studies on Xanthine Oxidase". Biochemical Journal. 19 (3): 507–512. doi:10.1042/bj0190507. PMC 1259209. PMID 16743533.
  8. ^ Dixon, Malcolm; Kleppe, Kjell (1965). "D-amino acid oxidase II. Specificity, competitive inhibition and reaction sequence". Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis. 96 (3): 368–382. doi:10.1016/0005-2787(65)90557-5.
  9. ^ Dixon, M. (1951). "Improved nomograms for manometer constants". Biochemical Journal. 48 (5): 575–580. doi:10.1042/bj0480575. PMC 1275377. PMID 14838904.
  10. ^ Dixon, M.; Hill, R.; Keilin, D. (1931). "The Absorption Spectrum of the Component c of Cytochrome". Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character. 109 (760): 29–34. Bibcode:1931RSPSB.109...29D. doi:10.1098/rspb.1931.0066.
  11. ^ Boursnell JC, Cohen JA, Dixon M, Francis GE, Greville GD, Needham DM, Wormall A (1946). "Studies on mustard gas (ββ'-dichlorodiethyl sulphide) and some related compounds". Biochemical Journal. 40 (5–6): 756–764. doi:10.1042/bj0400756. PMC 1270036. PMID 16748083.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ^ Dixon, M (1953). "The determination of enzyme inhibitor constants". Biochemical Journal. 55 (1): 170–171. doi:10.1042/bj0550170. PMC 1269152. PMID 13093635.
  13. ^ Dixon, M (1953). "The effect of pH on the affinities of enzymes for substrates and inhibitors". Biochemical Journal. 55 (1): 161–170. doi:10.1042/bj0550161. PMC 1269151. PMID 13093634.
  14. ^ Dixon, M; Webb, EC (1958). Enzymes (1st ed.). London: Longmans, Green, and Co.
  15. ^ Dixon, M; Webb, EC (1964). Enzymes (2nd ed.). London: Longmans, Green, and Co.
  16. ^ Dixon, M; Webb, EC; Thorne, CJR; Tipton, KF (1979). Enzymes (3rd ed.). London: Longmans Group. ISBN 978-0122183584.
  17. ^ Nomenclature Committee of the International Union of Biochemistry and Molecular Biology, Enzyme Nomenclature: https://www.qmul.ac.uk/sbcs/iubmb/enzyme/
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