Unidirectional inhibition and activation of ‘malic’ enzyme of <i>Solanum tuberosum</i> by <i>meso</i>-tartrate

Nascimento, KS; Davies, Daniel; Patil, K. D.

doi:10.1042/bj1490349

Cited by 5 publications

(3 citation statements)

References 14 publications

(8 reference statements)

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“…The different stereospecificity of the two dehydrogenases catalizing consecutive reactions is an exception to the generalization expressed by Davis et al [15,28], that NAD(P)-dependent dehydrogenases have the same stereospecificity when they catalyze consecutive steps in a metabolic sequence.…”

Section: Discussionmentioning

confidence: 88%

Enzymic Synthesis of Lignin Precursors

Wyrambik¹,

Grisebach²

1979

European Journal of Biochemistry

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Isoenzyme 2 of cinnamyl‐alcohol dehydrogenase from soybean suspension cultures was purified about 3800‐fold to apparent homogeneity by an improved purification procedure involving biospecific elution of the enzyme from a NADP+‐agarose column. On sodium dodecylsulfate gels the dehydrogenase showed only one protein band with Mr 40000 ± 500. The enzyme is strongly inhibited by thiol reagents. Various metal chelators as well as the non‐chelating 7,8‐benzoquinoline also inhibited enzyme activity. Inhibition by 10 mM 1,10‐phenanthroline could be partially reversed by addition of Zn2+. 1,10‐Phenanthroline and 7,8‐benzoquinoline are non‐competitive inhibitors with respect to NADP+. The presence of zinc in the dehydrogenase was proved by atomic absorption spectroscopy and by specific incorporation of 65Zn into the enzyme. In steady‐state kinetics inhibition patterns were obtained which are consistent with an ordered bi‐bi mechanism in which NADP(H) is the first substrate to bind and the last product released. The cinnamyl‐alcohol dehydrogenase belongs to the A‐specific dehydrogenases and removes the pro‐R hydrogen from coniferyl alcohol. The enzyme shows many similarities with alcohol dehydrogenases from horse and rat liver and from yeast.

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Section: Discussionmentioning

confidence: 88%

Enzymic Synthesis of Lignin Precursors

Wyrambik¹,

Grisebach²

1979

European Journal of Biochemistry

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“…We refer to this phenomenon as ‘forward inhibition’ throughout the manuscript. Preferential inhibition of enzyme activity in one direction has been discussed earlier [11] and is reported for few enzymes [12]–[17]. So far, sucrose synthase provides the lone example of a disulfide mediated reversible, unidirectional enzyme inhibition [16].…”

Section: Introductionmentioning

confidence: 83%

“…One-way inhibition in the presence of effectors, offers ways to modulate the enzyme function as and when desired. Such unidirectional inhibition has attracted some attention and is reported for a few enzymes [12]–[17]. Except sucrose synthase [16] all others are examples of non-covalent enzyme-effector interactions.…”

Section: Discussionmentioning

confidence: 99%

Mixed Disulfide Formation at Cys141 Leads to Apparent Unidirectional Attenuation of Aspergillus niger NADP-Glutamate Dehydrogenase Activity

2014

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NADP-Glutamate dehydrogenase from Aspergillus niger (AnGDH) exhibits sigmoid 2-oxoglutarate saturation. Incubation with 2-hydroxyethyl disulfide (2-HED, the disulfide of 2-mercaptoethanol) resulted in preferential attenuation of AnGDH reductive amination (forward) activity but with a negligible effect on oxidative deamination (reverse) activity, when monitored in the described standard assay. Such a disulfide modified AnGDH displaying less than 1.0% forward reaction rate could be isolated after 2-HED treatment. This unique forward inhibited GDH form (FIGDH), resembling a hypothetical ‘one-way’ active enzyme, was characterized. Kinetics of 2-HED mediated inhibition and protein thiol titrations suggested that a single thiol group is modified in FIGDH. Two site-directed cysteine mutants, C141S and C415S, were constructed to identify the relevant thiol in FIGDH. The forward activity of C141S alone was insensitive to 2-HED, implicating Cys141 in FIGDH formation. It was observed that FIGDH displayed maximal reaction rate only after a pre-incubation with 2-oxoglutarate and NADPH. In addition, compared to the native enzyme, FIGDH showed a four fold increase in K0.5 for 2-oxoglutarate and a two fold increase in the Michaelis constants for ammonium and NADPH. With no change in the GDH reaction equilibrium constant, the FIGDH catalyzed rate of approach to equilibrium from reductive amination side was sluggish. Altered kinetic properties of FIGDH at least partly account for the observed apparent loss of forward activity when monitored under defined assay conditions. In sum, although Cys141 is catalytically not essential, its covalent modification provides a striking example of converting the biosynthetic AnGDH into a catabolic enzyme.

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Glutamate dehydrogenase of the unicellular green alga Scenedesmus acutus

Shatilov

Sund

1983

Planta

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The coenzyme-non-specific glutamate dehydrogenase (EC 1.4.1.3) from Scenedesmus acutus in inhibited by p-hydroxymercuribenzoate only in the deamination reaction. From this result and from its stability in the presence of urea it is concluded that this enzyme exhibits and equilibrium between three conformations: aminating and deaminating conformations induced by NADH-2-oxoglutarate and NAD(+)-glutamate, respectively, and the "native" conformation in the absence of substrates.

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Unidirectional inhibition and activation of ‘malic’ enzyme of Solanum tuberosum by meso-tartrate

Cited by 5 publications

References 14 publications

Enzymic Synthesis of Lignin Precursors

Enzymic Synthesis of Lignin Precursors

Mixed Disulfide Formation at Cys141 Leads to Apparent Unidirectional Attenuation of Aspergillus niger NADP-Glutamate Dehydrogenase Activity

Glutamate dehydrogenase of the unicellular green alga Scenedesmus acutus

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