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KMID : 0380219940270060526
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Journal of Biochemistry and Molecular Biology
1994 Volume.27 No. 6 p.526 ~ p.533
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The Kinetic Mechanism and Chemical Modification of r-Aminobutyraldehyde Dehydrogenase from Soybean (Glycine max) Axes
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Abstract
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Abstract:
@EN Kinetics of the oxidation of γ-aminobutyraldehyde, catalyzed by NAD+-γ-aminobutyraldehyde dehydrogenase purified from axes of soybean (Glycine max), were analyzed by steady state initial velocity and product and dead-end inhibition studies.
In
initial velocity studies with NAD+ and γ-aminobutyraldehyde, Families of double reciprocal plots are linear and intersect at the left of he 1/v axis. NADH behaves as a mixed inhibitor against NAD+ and γ-aminobutyraldehyde, γ-aminobutyric acid
does
not inhibit the enzyme, even at concentractions as high as 50 mM. AMP is a mixed inhibitor against NAD+ and γ-aminobutyraldehyde, Since these data are consistent with an Iso Ordered Bi-Bi steady state mechanism, the data fit a model where NAD+
binds
first while NADH dissociates last. Inactivation of catalytic activity was observed when the enzyme was treated with the thiol group-directed reagent NEM. The initial reaction of this enzyme followed pseudo-first order kinetics and the value for
the
second order rate constant of inactivation was 296.3 M-1, min-1. The apparent order of reactin(N) was 0.77. Modification data suggest that two of four cysteine residues are associated with, or involved in, enzyme activity, and fluorescence
spectra
also
support this interpretation.
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KEYWORD
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