Abstract
L-Ornithine decarboxylase (EC 4.1.1.17) (ODC) catalyzes the conversion of L-ornithine to putrescine and CO2. ODC is dependent on pyridoxal 5′-phosphate (PLP) and thiol-reducing agents for activity (1). At least two key active site residues of ODC are known. Lysine 69 was recently identified as the residue in mouse ODC that forms a Schiff base with PLP and α-difluoromethyl-ornithine, an enzyme-activated irreversible inhibitor of ODC, forms adducts at both lysine 69 and cysteine 360 (2). It has been shown that mutation of cysteine 360 to alanine (C360A) results in an enzyme not only having greatly reduced activity, but the activity of this mutant is much more stable than wild-type ODC in the absence of dithiothreitol. The high dependence of ODC on thiol-reducing agents for activity is, therefore, likely to be a result of a need to maintain cysteine 360 in a reduced state (3).
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References
Pegg, A. E. and Williams-Ashman, H. G. (1981) Biosynthesis of putrescine, in Polyamines in Biology and Medicine (Morris, D. R. and Marton, L. J., eds.), Marcel Dekker Inc., New York, pp. 3–42.
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Coleman, C. S., Stanley, B. A., and Pegg, A. E. (1993) Effect of mutations at active site residues on the activity of ornithine decarboxylase and its inhibition by active site-directed irreversible inhibitors. J. Biol. Chem. 268, 24,572–24,579.
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© 1998 Humana Press Inc.
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Coleman, C.S., Pegg, A.E. (1998). Assay of Mammalian Ornithine Decarboxylase Activity Using [14C]Ornithine. In: Morgan, D.M.L. (eds) Polyamine Protocols. Methods in Molecular Biology™, vol 79. Humana Press. https://doi.org/10.1385/0-89603-448-8:41
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DOI: https://doi.org/10.1385/0-89603-448-8:41
Publisher Name: Humana Press
Print ISBN: 978-0-89603-448-8
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