Kinetic mechanism of NADP-malic enzyme from maize leaves

Spampinato, Claudia P.; Andreo, Carlos S.

doi:10.1007/bf00029456

Cited by 9 publications

(3 citation statements)

References 27 publications

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“…The mechanism of reaction proposed for NAD-ME2 (Figure 2A) resembles those reported for NADP-MEs from C 4 plants such as Pennisetum purpureum [30] and Zea mays [31], and from animal sources [32][33][34]. However, this mechanism differs from that suggested for other NAD-MEs, such as the isoforms from C. argentea [35] and A. suum [36,37], where the kinetic mechanisms were sequential with random binding of substrates and cofactors.…”

Section: Table 1 Inhibition Patterns Of a Thaliana Nad-me2mentioning

confidence: 51%

“…The catalysis by NAD(P)-MEs generally proceeds in three steps: dehydrogenation of L-malate to OAA; decarboxylation of OAA to enolpyruvate; and finally tautomerization of enolpyruvate to pyruvate [1]. As a possible consequence of this mechanism, NAD(P)-MEs can also catalyse alternative reactions such as the OAA decarboxylation and the pyruvate reductive carboxylation [31,41]. In our previous work, the OAA decarboxylating activity could not be detected under standard conditions for recombinant NAD-ME1, -ME2 and -MEH [17,18].…”

Section: A Thaliana Nad-mes Do Not Decarboxylate Oaa and Have Very Lmentioning

confidence: 99%

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NAD-malic enzymes of Arabidopsis thaliana display distinct kinetic mechanisms that support differences in physiological control

Tronconi

Wheeler

Maurino

et al. 2010

Biochemical Journal

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The Arabidopsis thaliana genome contains two genes encoding NAD-MEs [NAD-dependent malic enzymes; NAD-ME1 (TAIR accession number At4G13560) and NAD-ME2 (TAIR accession number At4G00570)]. The encoded proteins are localized to mitochondria and assemble as homo- and hetero- dimers in vitro and in vivo. In the present work, the kinetic mechanisms of NAD-ME1 and -ME2 homodimers and NAD-MEH (NAD-ME heterodimer) were studied as an approach to understand the contribution of these enzymes to plant physiology. Product-inhibition and substrate-analogue analyses indicated that NAD-ME2 follows a sequential ordered Bi-Ter mechanism, NAD being the leading substrate followed by L-malate. On the other hand, NAD-ME1 and NAD-MEH can bind both substrates randomly. However, NAD-ME1 shows a preferred route that involves the addition of NAD first. As a consequence of the kinetic mechanism, NAD-ME1 showed a partial inhibition by L-malate at low NAD concentrations. The analysis of a protein chimaeric for NAD-ME1 and -ME2 indicated that the first 176 amino acids are associated with the differences observed in the kinetic mechanisms of the enzymes. Furthermore, NAD-ME1, -ME2 and -MEH catalyse the reverse reaction (pyruvate reductive carboxylation) with very low catalytic activity, supporting the notion that these isoforms act only in L-malate oxidation in plant mitochondria. The different kinetic mechanism of each NAD-ME entity suggests that, for a metabolic condition in which the mitochondrial NAD level is low and the L-malate level is high, the activity of NAD-ME2 and/or -MEH would be preferred over that of NAD-ME1.

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Section: Table 1 Inhibition Patterns Of a Thaliana Nad-me2mentioning

confidence: 51%

Section: A Thaliana Nad-mes Do Not Decarboxylate Oaa and Have Very Lmentioning

confidence: 99%

NAD-malic enzymes of Arabidopsis thaliana display distinct kinetic mechanisms that support differences in physiological control

Tronconi

Wheeler

Maurino

et al. 2010

Biochemical Journal

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“…31,32 The kinetic mechanism for plant NADP-ME was studied only for photosynthetic chloroplastic NADP-ME from maize leaves and an ordered sequential mechanism was also determined. 35 In the present study, the regulation of cytosolic NADP-ME from tobacco leaves by cell metabolites, the most important of which were ATP, GTP and ADP (Table II), was also investigated. ATP was previously found to be an inhibitor for all NADP-ME isoenzymes of Arabidopsis thaliana and both chloroplastic and cytosolic ones of Nicotiana tabacum L. plants.…”

Section: Discussionmentioning

confidence: 99%

The regulation and catalytic mechanism of the NADP-malic enzyme from tobacco leaves

Doubnerová

Potůcková

Müller

et al. 2009

JSCS

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The non-photosynthetic NADP-malic enzyme EC 1.1.1.40 (NADP-ME), which catalyzes the oxidative decarboxylation of L-malate and NADP + to produce pyruvate and NADPH, respectively, and which could be involved in plant defense responses, was isolated from Nicotiana tabacum L. leaves. The mechanism of the enzyme reaction was studied by the initial rate method and was found to be an ordered sequential one. Regulation possibilities of purified cytosolic NADP-ME by cell metabolites were tested. Intermediates of the citric acid cycle (α-ketoglutarate, succinate, fumarate), metabolites of glycolysis (pyruvate, phosphoenolpyruvate, glucose-6-phosphate), compounds connected with lipogenesis (coenzyme A, acetyl-CoA, palmitoyl-CoA) and some amino acids (glutamate, glutamine, aspartate) did not significantly affect the NADP-ME activity from tobacco leaves. In contrast, macroergic compounds (GTP, ATP and ADP) were strong inhibitors of NADP-ME; the type of inhibition and the inhibition constants were determined in the presence of the most effective cofactors (Mn 2+ or Mg 2+ ), required by NADP-ME. Predominantly non-competitive type of inhibitions of NADP-ME with respect to NADP + and mixed type to L-malate were found.

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Lyases

Mahdi¹,

Kelly²

2000

Biotechnology

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Kinetic mechanism of NADP-malic enzyme from maize leaves

Cited by 9 publications

References 27 publications

NAD-malic enzymes of Arabidopsis thaliana display distinct kinetic mechanisms that support differences in physiological control

NAD-malic enzymes of Arabidopsis thaliana display distinct kinetic mechanisms that support differences in physiological control

The regulation and catalytic mechanism of the NADP-malic enzyme from tobacco leaves

Lyases

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