α-Keto Acid Dehydrogenase Complexes

Tsai, Chin‐Chun; Burgett, Michael W.; Reed, Lester J.

doi:10.1016/s0021-9258(19)43138-4

Cited by 144 publications

(9 citation statements)

References 13 publications

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“…From the results of these studies and those of the partial reaction between NADPH and Thio-NADP+, we establish the kinetic mechanism to be two-site uni-uni bi-bi ping-pong with separate sites for nucleotide oxidation and reductive amination which is consistent with the two-step hypothesis of Miller & Stadtman (1972). Other than multifunctional oxidoreductases (Bray, 1975), the only other enzymes to exhibit multisite ping-pong kinetics contain either biotin (Northrop, 1969;McClure et al, 1971;Barden et al, 1972) or a bound lipoic acid (Tsai et al, 1973) which provide a flexible arm to rotate or swing between the different sites. In glutamate synthase, electrons enter at one site and presumably flow to the other site via the iron-0006-2960/78/0417-5388S01.00/0 © 1978 American Chemical Society sulfur and flavin prosthetic groups; it is unclear whether an actual movable arm is needed for electron transfer between sites, as is presumably the case with the intersite group transfer observed with the biotin or lipoic acid containing systems.…”

supporting

confidence: 74%

Glutamate synthase: the kinetic mechanism of the enzyme from Escherichia coli W

Orme‐Johnson¹

1978

Biochemistry

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supporting

confidence: 74%

Glutamate synthase: the kinetic mechanism of the enzyme from Escherichia coli W

Orme‐Johnson¹

1978

Biochemistry

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“…N-OH-AA formation catalysed by isolated porcine heart PDHC is shown to proceed through a Ping Pong mechanism (Figure 1) which is also characteristic of the normal PDHC reaction [43]. Since the isolated component enzyme El shows the full N-OH-AA activity (Table 3 and Figure 4), El functions without any conformational changes affecting the activity due to it being detached from the other component enzymes (E2 and E3) of PDHC.…”

Section: Discussionmentioning

confidence: 87%

Formation of N-hydroxy-N-arylacetamides from nitroso aromatic compounds by the mammalian pyruvate dehydrogenase complex

Yoshioka

Uematsu

1993

Biochemical Journal

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Bovine, human and porcine heart mitochondria and isolated porcine heart pyruvate dehydrogenase complex (PDHC) pyruvate-dependently form N-hydroxy-N-arylacetamides from nitroso aromatic compounds, including carcinogenic 4-biphenyl and 2-fluorenyl derivatives. The PDHC-catalysed formation of N-hydroxyacetanilide (N-OH-AA) from nitrosobenzene (NOB), through a Ping Pong mechanism, is optimum at pH 6.8 and is accelerated by thiamin pyrophosphate, but is inhibited by thiamin thiazolone pyrophosphate and ATP. Km pyruvate in the reaction is independent of pH over the range tested, whereas KmNOB increases at lower pH, owing to ionization of an active-site functional group of pKa 6.3. The enzymic ionization decreases log (Vmax/KmNOB). Isolated pyruvate dehydrogenase (E1), a constitutive enzyme of PDHC, forms N-OH-AA by itself and has comparable kinetic parameters to those of the PDHC-catalysed N-OH-AA formation. The catalytic efficiency of PDHC in the formation of N-hydroxy-N-arylacylamides, due to the steric limitation of the active site of E1, is lowered both by bulky alkyl groups of alpha-oxo acids and by p-substituents (but not an o-substituent) on nitrosobenzenes. These nitroso compounds serve as electrophiles in the reaction in which the reductive acetylation step is rate-limiting. The reaction mechanism and other factors affecting N-hydroxy-N-arylacylamide formation are discussed.

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“…This kind of kinetic interplay between separate catalytic sites is referred to as a hybrid or nonclassical ping-pong, or rapid equilibrium random ping-pong, mechanism. Other examples of enzymes exhibiting this kind of kinetics are methylmalonyl-CoA:pyruvate carboxytransferase (Northrop, 1969), pyruvate carboxylase (Barden et al, 1972), pyruvate dehydrogenase (Tsai et al, 1973), sulfite oxidase (Kessler & Rajagopalan, 1974), -ketoglutarate dehydrogenase (Hamada et al, 1975) and the rate of succinate oxidation (A). The experiments were carried out essentially as described before (Hatefi et al, 1982) in the presence of 5 mM succinate, 1.1 mM ADP, 20 mM potassium phosphate, pH 7.5, and 0.1 mg of SMP/mL.…”

Section: Resultsmentioning

confidence: 99%

Modulation of the kinetics and the steady-state level of intermediates of mitochondrial coupled reactions by inhibitors and uncouplers

Yagi¹,

Matsuno‐Yagi²,

Vik³

et al. 1984

Biochemistry

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In oxidative phosphorylation and ATP-driven uphill electron transfer from succinate to NAD, double-reciprocal plots of rates vs. substrate concentrations of the energy-driven reactions are a family of parallel lines at several fixed subsaturating concentrations of the substrates or at several moderate concentrations of the inhibitors of the energy-yielding reactions. Thus, as shown elsewhere [Hatefi, Y., Yagi, T., Phelps, D. C., Wong, S.-Y., Vik, S. B., & Galante, Y. M. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 1756-1760], partial uncoupling decreases the Vappmax and increases the Kappm of the substrates of the energy-driven reactions, resulting in a decrease of Vmax/Km as a function of increased uncoupling. However, partial limitation of the flow rates of the energy-yielding reactions decreases both the Vappmax and the Kappm of the substrates of the energy-driven reactions, resulting in no change in Vmax/Km. This is true as long as the rate limitation is moderate (e.g., less than 60%), under which conditions the steady-state membrane potential (delta psi) remains essentially unchanged. At high inhibition of the energy-yielding reactions, or at moderate inhibition in the presence of low levels of an uncoupler to cause partial uncoupling, then the family of double-reciprocal plots is no longer parallel and tends to converge toward the left. Under these conditions, steady-state delta psi and Vmax/Km also decrease as inhibition is increased. The relationship between the magnitude of steady-state delta psi and the rate of the energy-driven reaction was studied in oxidative phosphorylation, ATP-driven electron transfer from succinate to NAD, and respiration-driven uniport calcium transport by intact mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)

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α-Keto Acid Dehydrogenase Complexes

Cited by 144 publications

References 13 publications

Glutamate synthase: the kinetic mechanism of the enzyme from Escherichia coli W

Glutamate synthase: the kinetic mechanism of the enzyme from Escherichia coli W

Formation of N-hydroxy-N-arylacetamides from nitroso aromatic compounds by the mammalian pyruvate dehydrogenase complex

Modulation of the kinetics and the steady-state level of intermediates of mitochondrial coupled reactions by inhibitors and uncouplers

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