Activity, Location and Role of NAD Malic Enzyme in Leaves With C4-Pathway Photosynthesis

1974 ◽  
Vol 1 (3) ◽  
pp. 357 ◽  
Author(s):  
MD Hatch ◽  
T Kagawa
Keyword(s):  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Integral Function ◽  
Bundle Sheath ◽  
Leaf Extracts ◽  
Acetyl Coa ◽  
Mesophyll Cells ◽  
C3 Species ◽  
C4 Pathway ◽  
Malic Enzyme Activity

C4 acid decarboxylation in many C4-pathway species is accounted for either by an NADP-specific malic enzyme or phosphoenolpyruvate carboxykinase but a major group lack these enzymes. The present paper provides evidence for the mediation of C4 acid decarboxylation in this group by an NAD malic enzyme located in bundle sheath mitochondria. This enzyme was most active with NAD and Mn2+ and, depending upon its source, activity was stimulated 5- to 15-fold by low con- centrations of CoA or acetyl-CoA. The activity in leaf extracts was 20-50 times that found in other groups of C4 species or in C3 species and was commensurate with the enzyme having an integral function in photosynthesis. For most species showing high NAD malic enzyme activity there was little activity when Mg2+ replaced Mn2+ and the low activity recorded with NADP was not activated by CoA or acetyl-CoA. In others there was an activator-dependent rate with NADP equivalent to 25-30% of the rate with NAD. Evidence for the location of the NAD malic enzyme in bundle sheath mitochondria is provided. On the basis of these and earlier studies a detailed scheme is proposed to account for decarboxylation of aspartate derived from mesophyll cells.

Subdivision of C4-Pathway Species Based on Differing C4 Acid Decarboxylating Systems and Ultrastructural Features

1975 ◽  
Vol 2 (2) ◽  
pp. 111 ◽  
Author(s):  
MD Hatch ◽  
T Kagawa ◽  
S Craig
Keyword(s):  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Bundle Sheath ◽  
Intracellular Location ◽  
Bundle Sheath Cells ◽  
C4 Pathway ◽  
Malic Enzyme Activity ◽  
Mitochondrial Respiratory Enzyme ◽  
The Relationship ◽  
Sheath Cells

A selection of C4 species was surveyed to determine the relationship between their content of C4 acid decarboxylating enzymes, the activities of several other enzymes implicated in the C4 pathway, and their anatomical and ultrastructural features. The species examined clearly fell into three groups according to whether they contained high levels of either NADP malic enzyme (EC 1.1.1.40), phosphoenolpyruvate carboxykinase (EC 4.1.1.49) or NAD malic enzyme (EC 1.1 .1.39). The occurrence of high NADP malic enzyme activity was always associated with higher NADP malate dehydrogenase activity, while those species distinguished by high activities of either of the other two decarboxylases invariably contained high aspartate aminotransferase and alanine amino- transferase activities. Each of these decarboxylating enzymes was located in bundle sheath cells. NAD malic enzyme, but not phosphoenolpyruvate carboxykinase, was associated with mitochondria. Light and electron micrographs revealed differences between these groups with respect to the intracellular location of chloroplasts and mitochondria in bundle sheath cells, and the content and ultrastructure of mitochondria. The trend was for species with high NAD malic enzyme to contain the most mitochondria in the bundle sheath cells with apparently the most extensively developed cristae membrane systems. However, mitochondrial respiratory enzyme activities were similar for the three groups of species. The basic similarities and differences between the three groups of C4 plants distinguished by their differing C4 acid decarboxylating systems are discussed, and schemes for the probable photosynthetic reactions in bundle sheath cells are presented. A nomenclature to distinguish between these groups is proposed.

Photosynthesis in Phosphoenolpyruvate Carboxykinase-Type C4 Species: Properties of Nad-Malic Enzyme From Urochloa panicoides

1987 ◽  
Vol 14 (5) ◽  
pp. 517 ◽  
Author(s):  
JN Burnell
Keyword(s):  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Bundle Sheath ◽  
Photosynthetic Pathway ◽  
C4 Plant ◽  
C4 Species ◽  
Absolute Requirement ◽  
Pep Carboxykinase ◽  
Fructose 1,6 Bisphosphate ◽  
Regulatory Properties

NAD-malic enzyme (EC 1.1.1.39) was purified from bundle sheath strands of Urochloa panicoides (a phosphoenolpyruvate carboxykinase-type C4 plant) and its kinetic and regulatory properties were investigated. The native enzyme has a molecular weight of about 470 000 and is an octomer composed of two slightly different monomers which occur in a 1 : 1 ratio. The enzyme has an absolute requirement for Mn2+, is stimulated by CoA, acetyl CoA, fructose 1,6-bisphosphate and SO42- and is inhibited by HCO3, oxaloacetate, 2-oxoglutarate and pyruvate. The enzyme is shown to be localised in the mito- chondria. The purified NAD-malic enzyme is unable to catalyse the carboxylation of pyruvate according to the reverse reaction. These findings are discussed in relation to the C4 photosynthetic pathway and its possible role in PEP carboxykinase-type C4 plants.

Photosynthesis in Gomphrena celosioides and Its Classification Amongst C4-pathway Plants

1976 ◽  
Vol 3 (6) ◽  
pp. 863 ◽  
Author(s):  
E Repo ◽  
MD Hatch
Keyword(s):  
Malate Dehydrogenase ◽  
Malic Enzyme ◽  
Bundle Sheath ◽  
Mesophyll Cells ◽  
C4 Species ◽  
Bundle Sheath Cells ◽  
Major Route ◽  
Gomphrena Celosioides ◽  
A Minor ◽  
Sheath Cells

Monocotyledonous C4 species classified as NADP-ME-type transfer malate from mesophyll to bundle sheath cells where this acid is decarboxylated via NADP malic enzyme (EC 1.1.1.40) to yield pyruvate and CO2. The dicotyledon G. celosioides is most appropriately classified in thls group on the basis of high leaf activities of NADP malic enzyme and NADP malate dehydrogenase (EC 1.1.1.82). However, this species contains high aspartate aminotransferase (EC 2.6.1.1) and alanine aminotransferase (EC 2.6.1.2) activities and centripetally located bundle sheath chloroplasts, features more typical of other groups of C4 species that cycle aspartate and alanine between mesophyll and bundle sheath cells. During the present study, we found that these aminotransferases and NADP malate dehydrogenase were predominantly located in mesophyll cells, that malate was the major C4 acid labelled when leaves were exposed to 14CO2, and that label was initially lost most rapidly from the C-4 of malate during a chase in 12CO2. These results are consistent with the major route of photosynthetic metabolism being the same as that operative in other NADP-ME-type species, although this may be supplemented by a minor route utilizing aspartate. In contrast to monocotyledonous NADP-ME-type C4 species, isolated bundle sheath cells from G. celosioides were capable of rapid photoreduction of NADP as judged by products formed during assimilation of 14CO2 and their capacity for light-dependent oxygen evolution. This was related to a relatively high frequency of single unstacked granum in the chloroplasts of these cells.

Mitochondrial Respiration in Relation to Photosynthetic C4 Acid Decarboxylation in C4 Species

1996 ◽  
Vol 23 (1) ◽  
pp. 1 ◽  
Author(s):  
A Agostino ◽  
HW Heldt ◽  
MD Hatch
Keyword(s):  
Malic Enzyme ◽  
Type Species ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Alternative Oxidase ◽  
Bundle Sheath ◽  
C4 Species ◽  
Bundle Sheath Cells ◽  
A Minor ◽  
Mitochondrial Malate Dehydrogenase ◽  
Sheath Cells

Certain respiratory features of bundle sheath cells isolated from the C4 species Urochloa panicoides (phosphoenolpyruvate carboxykinase (PCK)-type)), Panicum miliaceum (NAD malic enzyme (NAD-ME)-type) and Zea mays (NADP malic enzyme (NADP-ME)-type) were examined in relation to the requirements of the C4 acid decarboxylation step of C4 photosynthesis. Cells from both PCK-type and NAD-ME-type species showed high rates of malate-dependent respiration; with ADP or uncoupler the rates were in the range 2-3 μatom O min-1 mg-1 chlorophyll, about 5-10-times the rates with other respiratory substrates. Studies with inhibitors of cytochrome oxidase and the alternative oxidase indicated negligible alternative oxidase-mediated malate respiration in cells from Z. mays, a minor contribution in U. panicoides cells, but possibly a major role for this oxidase in the respiration of P. miliaceum cells. These differences were related to the different roles of respiration in photosynthetic C4 acid decarboxylation. Oxaloacetate strongly suppressed malate-dependent respiration in P. miliaceum bundle sheath cells but not in U. panicoides cells. This difference in the response to oxaloacetate was not due to different kinetic features of the mitochondrial malate dehydrogenase but was apparently largely due to the much lower activity of the enzyme in U. panicoides bundle sheath mitochondria. We propose that insensitivity of respiration to oxaloacetate in bundle sheath cells of PCK-type species may be essential for maintaining the C4 acid decarboxylation process. The reverse may be true for NAD-ME- type species.

scholarly journals Developmental Effects on Relative Use of PEPCK and NADP-ME Pathways of C4 Photosynthesis in Maize

2021 ◽  
Author(s):  
Jennifer J Arp ◽  
Shrikaar Kambhampati ◽  
Kevin Chu ◽  
Somnath Koley ◽  
Lauren M Jenkins ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Leaf Development ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Photosynthesis ◽  
Leaf Age ◽  
Bundle Sheath ◽  
Decarboxylase Activity ◽  
Mesophyll Cells ◽  
Source To Sink ◽  
Canopy Position

C4 photosynthesis is an adaptive photosynthetic pathway which concentrates CO2 around Rubisco in specialized bundle sheath cells to reduce photorespiration. Historically, the pathway has been characterized into three different subtypes based on the decarboxylase involved, although recent work has provided evidence that some plants can use multiple decarboxylases, with maize in particular using both the NADP-malic enzyme (NADP-ME) pathway and phosphoenolpyruvate carboxykinase (PEPCK) pathway. Parallel C4 pathways could be advantageous in balancing energy and reducing equivalents between bundle sheath and mesophyll cells, in decreasing the size of the metabolite gradients between cells and may better accommodate changing environmental conditions or source to sink demands on growth. The enzyme activity of C4 decarboxylases can fluctuate with different stages of leaf development, but it remains unclear if the pathway flexibility is an innate aspect of leaf development or an adaptation to the leaf microenvironment that is regulated by the plant. In this study, variation in the two C4 pathways in maize were characterized at nine plant ages throughout the life cycle. Two positions in the canopy were examined for variation in physiology, gene expression, metabolite concentration, and enzyme activity, with particular interest in asparagine as a potential regulator of C4 decarboxylase activity. Variation in C4 and C3 metabolism was observed for both leaf age and canopy position, reflecting the ability of C4 pathways to adapt to changing microenvironments.

Preferential C4-dicarboxylic acid synthesis, the postillumination CO2 burst, carboxyl transfer step, and grana configurations in plants with C4-photosynthesis

1970 ◽  
Vol 48 (10) ◽  
pp. 1795-1800 ◽  
Author(s):  
W. J. S. Downton
Keyword(s):  
Malic Enzyme ◽  
Calvin Cycle ◽  
Reducing Power ◽  
Acid Synthesis ◽  
Bundle Sheath ◽  
Short Term ◽  
Transfer Step ◽  
Malate Transport ◽  
Malic Enzyme Activity ◽  
Sheath Cells

An oxygen-insensitive postillumination CO2 burst occurs in many plants with the C4-pathway of photosynthesis. C4-species with a postillumination burst synthesize mainly aspartate during very short term photosynthesis and have low levels of 'malic' enzyme (EC. 1.1.1.40) activity. It is postulated that the burst is CO2 which normally participates in the carboxyl transfer step of C4-photosynthesis. The burst is absent in C4-species that produce mainly malate in short-term photosynthesis. This group of plants has very high 'malic' enzyme activity. Transport of malate to the bundle sheath layer and its metabolism by 'malic' enzyme provides reducing power (NADPH2) as well as CO2 to the Calvin cycle. This combination of products may attenuate the postillumination burst. Some malate formers show extreme grana reduction in bundle sheath chloroplasts which, is associated with a low capacity for generating reducing power. Malate transport compensates for this lack of reducing power in sheath cells with agranal chloroplasts. Transport of aspartate or oxaloacetate to the sheath cells does not transfer reducing power. The sheath chloroplasts of aspartate formers have well-developed grana but some reduction in grana within mesophyll chloroplasts is apparent in certain species. This reduction may reflect a low demand for reducing power where the major C4-acid synthesized is aspartate rather than malate.

scholarly journals Respiratory and C4-photosynthetic NAD-malic enzyme coexist in bundle sheath cells mitochondria and evolved via association of differentially adapted subunits

2021 ◽  
Author(s):  
Meike Huedig ◽  
Marcos A Tronconi ◽  
Juan P Zubimendi ◽  
Tammy L Sage ◽  
Gereon Poschmann ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Malic Enzyme ◽  
Tricarboxylic Acid Cycle ◽  
Catalytic Efficiency ◽  
Biochemical Properties ◽  
Bundle Sheath ◽  
Α Subunit ◽  
C4 Species ◽  
C3 Species ◽  
C4 Evolution

In different lineages of Cleomaceae, NAD-malic enzyme (NAD-ME) was independently co-opted to participate in C4 photosynthesis. In the C4 Cleome species Gynandropsis gynandra and Cleome angustifolia, all NAD-ME genes (NAD-MEα, NAD-MEβ1, and NAD-MEβ2) were affected by C4 evolution and are expressed at higher levels than their orthologs in the C3 Cleome species Tarenaya hassleriana. In the latter C3 species, the NAD-ME housekeeping function is performed by two heteromers, NAD-MEα/β1 and NAD-MEα/β2, with similar biochemical properties. In both C4 species analyzed, this role is restricted the NAD-MEα/β2 heteromer. In the C4 species, NAD-MEα/β1 is exclusively present in the leaves, where it accounts for most of the enzymatic activity. GgNAD-MEα/β1 exhibits high catalytic efficiency and is differentially activated by the C4 intermediate aspartate, confirming its role as the C4-decarboxylase. During C4 evolution, GgNAD-MEβ1and CaNAD-MEβ1 lost their catalytic activity; their contribution to enzymatic activity results from a stabilizing effect on the associated α-subunit. We conclude that in bundle sheath cell mitochondria of C4 Cleome species, the functions of NAD-ME as C4 photosynthetic decarboxylase and as a tricarboxylic acid cycle-associated housekeeping enzyme coexist and are performed by isoforms that combine the same α subunit with differentially adapted β subunits.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

scholarly journals Four Mutant Alleles Elucidate the Role of the G2 Protein in the Development of C4 and C3 Photosynthesizing Maize Tissues

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 787-797
Author(s):  
Lizzie Cribb ◽  
Lisa N Hall ◽  
Jane A Langdale
Keyword(s):  
Cell Types ◽  
Bundle Sheath ◽  
Primary Role ◽  
Ribulose Bisphosphate Carboxylase ◽  
Sheath Cell ◽  
Mesophyll Cells ◽  
Phenotypic Data ◽  
Bisphosphate Carboxylase ◽  
Bundle Sheath Cell

Abstract Maize leaf blades differentiate dimorphic photosynthetic cell types, the bundle sheath and mesophyll, between which the reactions of C4 photosynthesis are partitioned. Leaf-like organs of maize such as husk leaves, however, develop a C3 pattern of differentiation whereby ribulose bisphosphate carboxylase (RuBPCase) accumulates in all photosynthetic cell types. The Golden2 (G2) gene has previously been shown to play a role in bundle sheath cell differentiation in C4 leaf blades and to play a less well-defined role in C3 maize tissues. To further analyze G2 gene function in maize, four g2 mutations have been characterized. Three of these mutations were induced by the transposable element Spm. In g2-bsd1-m1 and g2-bsd1-s1, the element is inserted in the second intron and in g2-pg14 the element is inserted in the promoter. In the fourth case, g2-R, four amino acid changes and premature polyadenylation of the G2 transcript are observed. The phenotypes conditioned by these four mutations demonstrate that the primary role of G2 in C4 leaf blades is to promote bundle sheath cell chloroplast development. C4 photosynthetic enzymes can accumulate in both bundle sheath and mesophyll cells in the absence of G2. In C3 tissue, however, G2 influences both chloroplast differentiation and photosynthetic enzyme accumulation patterns. On the basis of the phenotypic data obtained, a model that postulates how G2 acts to facilitate C4 and C3 patterns of tissue development is proposed.

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