Kinetics and thermodynamics of ethanol oxidation catalyzed by genetic variants of the alcohol dehydrogenase from Drosophila melanogaster and D. simulans

• Published in: Biochimica et biophysica acta Vol. 967; no. 2; pp. 224 - 233
• Main Authors: Heinstra, P.W.H, Thorig, G.E.W, Scharloo, W, Drenth, W, Nolte, R.J.M
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 17.11.1988; North-Holland
• Subjects: alcohol dehydrogenase; Alcohol Dehydrogenase - genetics; Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Drosophila; Drosophila - enzymology; Drosophila - genetics; Drosophila melanogaster; Drosophila melanogaster - enzymology; Drosophila melanogaster - genetics; Enzymes and enzyme inhibitors; Ethanol - metabolism; evolution; Fundamental and applied biological sciences. Psychology; genetic variation; Isoenzymes - genetics; Isoenzymes - metabolism; Kinetics; Oxidation-Reduction; Oxidoreductases; Thermodynamics; Purification; Ethanol; Enzyme; Insecta; Enthalpy; Primary structure; Entropy; Alcohol dehydrogenase; Drosophilidae; Thermodynamics; Arthropoda; Oxidation; Kinetics; Invertebrata; Drosophila melanogaster; Diptera
• ISSN: 0006-3002; 1878-2434

Four naturally occurring variants of the alcohol dehydrogenase enzyme (ADH; EC 1.1.1.1) from Drosophila melanogaster and D. simulans, with different primary structures, have been subjected to kinetic studies of ethanol oxidation at five temperatures. Two amino acid replacements in the N-terminal region which distinguish the ADH of D. simulans from the three ADH allozymes of D. melanogaster generate a significantly different activation enthalpy and entropy, and Gibbs free energy change. The one or two amino acid replacements in the C-terminal region between the ADH allozymes of D. melanogaster do not have such clear-cut efects. All four ADH variants show highly negative activation entropies. Sarcosine oxidation by the ADH-71k variant of D. melanogaster has an activation energy barrier similar to that of ethanol oxidation. Three amino acid differences between the ADH of D. simulans and the ADH of D. simulans and the ADH-F variant of D. melanogaster influence the k cat and k cat / Km(eth) constant by a maximum factor of about 2 and 2.5, respectively, over the whole temperature range. Product inhibition patterns suggest a 'rapid equilibrium random' mechanism of ethanol oxidation by the ADH-71k, and the ADH of D. simulans.