TY - JOUR
T1 - Conjugated αketo acids as mechanism-based inactivators of brewer's yeast pyruvate decarboxylase electronic effects of substituents and detection of a long-lived intermediate
AU - Jordan, Frank
AU - Adams, Joseph
AU - Farzami, Bijan
AU - Kudzin, Zbigniew H.
N1 - Funding Information:
The authors are grateful to the National Science Foundation (Grant PCM 8217100), the Rutgers University Busch Fund, MBRS grant (M. Nathanson, P.I.) and Hoffmann-La Roche Inc., Nutley, NJ, for financial support; to Dr. F. J. Scheidl of
PY - 1986
Y1 - 1986
N2 - A series of phenyl substituted E-4-phenyl-2-keto-3-butenoic acid derivatives were synthesized (p-Cl, m-Cl, P-NO2, m-NO2, o-NO2, 3,4-Cl2 2,6-Cl2, p-CH3O, P-(CH3)3N) and tested as potential irreversible inhibitors of brewer's yeast pyruvate decarboxylase (EC 4.1.1.1). All those derivatives with electron withdrawing substituents were found to be time-dependent inactivators of the enzyme, unlike the P-CH3O- and p-(CH3)2N derivatives. Detailed kinetic studies with the m-nitro derivative (the most potent inhibitor) indicated that this compound formed reversible complexes with the enzyme at two sites (supposed regulatory and catalytic with Ki values of 0.026 and 0.13 mM, respectively) prior to irreversible inactivation of the enzyme. In addition, concurrently with the inactivation, addition of the m-NO2 derivative to the enzyme produced a new VIS absorbance with λmax near 430 nm. This absorbance was attributed to the enzyme-bound enamine intermediate. The time course of formation and disappearance of the intermediate could be determined and provided detailed information about the mechanism of the enzyme.
AB - A series of phenyl substituted E-4-phenyl-2-keto-3-butenoic acid derivatives were synthesized (p-Cl, m-Cl, P-NO2, m-NO2, o-NO2, 3,4-Cl2 2,6-Cl2, p-CH3O, P-(CH3)3N) and tested as potential irreversible inhibitors of brewer's yeast pyruvate decarboxylase (EC 4.1.1.1). All those derivatives with electron withdrawing substituents were found to be time-dependent inactivators of the enzyme, unlike the P-CH3O- and p-(CH3)2N derivatives. Detailed kinetic studies with the m-nitro derivative (the most potent inhibitor) indicated that this compound formed reversible complexes with the enzyme at two sites (supposed regulatory and catalytic with Ki values of 0.026 and 0.13 mM, respectively) prior to irreversible inactivation of the enzyme. In addition, concurrently with the inactivation, addition of the m-NO2 derivative to the enzyme produced a new VIS absorbance with λmax near 430 nm. This absorbance was attributed to the enzyme-bound enamine intermediate. The time course of formation and disappearance of the intermediate could be determined and provided detailed information about the mechanism of the enzyme.
KW - Enamine
KW - Mechanism-based inactivator
KW - Yeast pyruvate decarboxylase
KW - αketo acids
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U2 - 10.3109/14756368609020112
DO - 10.3109/14756368609020112
M3 - Article
C2 - 3334240
AN - SCOPUS:0022946325
SN - 1475-6366
VL - 1
SP - 139
EP - 149
JO - Journal of Enzyme Inhibition and Medicinal Chemistry
JF - Journal of Enzyme Inhibition and Medicinal Chemistry
IS - 2
ER -