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.

Phosphoenolpyruvate Carboxykinase in C4 Plants: Its Role and Regulation

1997 ◽  
Vol 24 (4) ◽  
pp. 459 ◽  
Author(s):  
Robert P. Walker ◽  
Richard M. Acheson ◽  
László I. Técsi ◽  
Richard C. Leegood
Keyword(s):  
Molecular Mass ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Plants ◽  
Panicum Maximum ◽  
C4 Plant ◽  
Cam Plants ◽  
Crude Extracts ◽  
High Concentrations ◽  
Regulatory Properties

Some of the recent findings which revise our view of the role and regulation of phosphoenolpyruvate carboxykinase (PEPCK) in C4 plants are discussed. Evidence is presented that PEPCK is present at appreciable activities in the bundle-sheath of some NADP-malic enzyme-type C4 plants, such as maize, but it was not detectable in NAD-malic enzyme-type C4 plants. PEPCK is rapidly inactivated in crude extracts of leaves of the C4 plant, Panicum maximum. This inactivation could be prevented by high concentrations of dithiothreitol or by the inclusion of ADP or ATP, suggesting the involvement of thiols at the active site. PEPCK is also subject to rapid proteolysis in crude extracts of a range of C4 plants, resulting in cleavage to a smaller (62 kDa) form. This can be reduced by extraction at high pH and by the inclusion of SDS, but it means that intact PEPCK has never been purified from a C4 plant. The molecular mass of PEPCK varies considerably in C4 plants, unlike C3 and CAM plants in which it is usually 74 kDa. PEPCK is phosphorylated during darkness (and reversed by light) in some C4 plants with PEPCK of a larger molecular mass, such as Panicum maximum (71 kDa), but it was not phosphorylated in the PEPCK-type C4 plant, Sporobolus pyramidalis (69 kDa). The known regulatory properties of PEPCK are discussed in relation to its role in C4 photosynthesis, in particular its sensitivity to regulation by adenylates and by Mn2+.

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.

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.

Photosynthetic Mechanisms of Weeds in Taiwan

1993 ◽  
Vol 20 (6) ◽  
pp. 757 ◽  
Author(s):  
CH Lin ◽  
YS Tai ◽  
DJ Liu ◽  
MSB Ku
Keyword(s):  
Malic Enzyme ◽  
Co2 Fixation ◽  
C4 Photosynthesis ◽  
C3 Plants ◽  
C4 Species ◽  
On This Island ◽  
High Precipitation ◽  
Biochemical Analyses ◽  
Pep Carboxykinase ◽  
First Time

One hundred and one species (in 36 families) of weeds on cultivated land in Taiwan were investigated for the occurrence of Kranz leaf anatomy and activities of key enzymes of C4 photosynthesis to determine their photosynthetic mechanisms. Based on the anatomical and biochemical analyses, 75 species were found to possess the C3 and 26 species the C4 pathway of photosynthetic CO2 fixation. Among the 26 C4 species, 15 species are in Gramineae, 6 in Cyperaceae, 2 each in Euphorbiaceae and Amaranthaceae, and 1 in Portulacaceae. Two C4 species in the Gramineae, namely Digitaria radicosa (Presl) Miq. and Sporobolus fertilis (Steud.) Clayton, were recorded as C4 plants for the first time. The biochemical subdivisions of these C4 weeds were also determined. As in the natural C4 populations, the NADP-malic enzyme subtype of C4 photosynthesis dominates the list of C4 weeds on this island (62%), while the PEP carboxykinase subtype is relatively rare (12%). NAD-malic enzyme subtype has an intermediate representation (26%). The high proportion of weeds in Taiwan being C3 plants is noteworthy, and it may be accounted for by the high precipitation in this subtropical island.

Purification and Properties of Phosphoenolpyruvate Carboxykinase from C4 Plants

1986 ◽  
Vol 13 (5) ◽  
pp. 577 ◽  
Author(s):  
JN Burnell
Keyword(s):  
Molecular Weight ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Plants ◽  
Kinetic Properties ◽  
Panicum Maximum ◽  
Ph Optimum ◽  
Wide Ph Range ◽  
Pep Carboxykinase ◽  
Nucleotide Specificity ◽  
Fructose 1,6 Bisphosphate

Phosphoenolpyruvate (PEP) carboxykinase (EC 4.1.1.49) from the leaves of Urochloa panicoides, Chloris gayana and Panicum maximum has been purified to homogeneity and its properties determined. The enzyme from all three PEP carboxykinase-type C4 plants have similar physical and kinetic properties. The native enzyme has a molecular weight of 380 000 and its monomeric molecular weight is about 64 000, suggesting the enzyme is hexameric. It is active over a wide pH range and has a pH optimum between 7.4 and 8.2, has a wide nucleotide specificity, has an absolute requirement for Mn2+ and is stimulated by C-. The enzyme is inhibited by 3-phosphoglyceric acid, fructose 6-phosphate and fructose 1,6-bisphosphate; the mechanism of inhibition is discussed. The purified PEP carboxykinase is unable to catalyse the conversion of oxaloacetate to pyruvate, nor does it possess pyruvate kinase activity. These findings are discussed in relation to the C4 photosynthetic pathway operating in PEP carboxykinase-type C4 plants.

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.

C4 Acid Decarboxylation Enzymes and Anatomy in Sedges (Cyperaceae): First Record of NAD-Malic Enzyme Species

1987 ◽  
Vol 14 (6) ◽  
pp. 719 ◽  
Author(s):  
JJ Bruhl ◽  
NE Stone ◽  
PW Hattersley
Keyword(s):  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
First Record ◽  
The Other ◽  
Photosynthetic Pathway ◽  
The Family ◽  
Enzyme Species

The activities of C4 acid decarboxylation enzymes (NAD-malic enzyme, NADP-malic enzyme, and phosphoenolpyruvate carboxykinase), and the anatomy of photosynthetic organs (leaves, culms, bracts) were investigated in 30 species from 12 C3, C4, and mixed (C3+C4) genera of sedges. The sample incorporated representatives of the three previously known C4 anatomical types in the family (fimbristyloid, chlorocyperoid, and rhynchosporoid), and of six genera previously uninvestigated biochemically, including Eleocharis (six species). Eleocharis is variable for photosynthetic pathway: three species proved to be C3, two C4 (E. caespitosissima Baker and E. retroflexa (Poir.) Urban), and one (E. pusilla R. Br.) may be a C3-C4 intermediate. The C4 Eleocharis spp. exhibit a C4 anatomy ('eleocharoid') hitherto undescribed, and are NAD-ME type, in contrast to species of the other three C4 anatomical types examined in this and previous studies, which are all NADP-ME type. The PCK type remains unrecorded in the family.

scholarly journals Isolation and properties of a ‘malic’ enzyme from cauliflower bud mitochondria

1971 ◽  
Vol 122 (4) ◽  
pp. 495-501 ◽  
Author(s):  
A. R. Macrae
Keyword(s):  
Malic Enzyme ◽  
Tricarboxylic Acid Cycle ◽  
Decarboxylase Activity ◽  
Enzyme Preparations ◽  
Ph Values ◽  
Low Concentrations ◽  
Absolute Requirement ◽  
Nad Oxidoreductase ◽  
Regulatory Properties

1. A ‘malic’ enzyme [l-malate–NAD oxidoreductase (decarboxylating), EC 1.1.1.39] has been isolated from cauliflower bud mitochondria and partially purified. 2. The enzyme is specific for l-malate and has an absolute requirement for either Mn2+, Co2+ or Mg2+. 3. The enzyme shows activity with both NAD+ and NADP+, but NAD+ is the preferred cofactor. 4. No appreciable oxaloacetate decarboxylase activity is present in the enzyme preparations even at low pH values. 5. The enzyme is inhibited by NADH and by oxaloacetate and stimulated by SO42− and by low concentrations of CoA. 6. The regulatory properties of the enzyme support the proposed role of the enzyme in the utilization of tricarboxylic acid-cycle acids for energy production when glycolysis is suppressed.

Aspartate Decarboxylation in Bundle Sheath Cells of Zea mays and Its Possible Contribution to C3 Photosynthesis

1981 ◽  
Vol 8 (2) ◽  
pp. 237 ◽  
Author(s):  
KSR Chapman ◽  
MD Hatch
Keyword(s):  
Zea Mays ◽  
Oxygen Evolution ◽  
Malic Enzyme ◽  
Bundle Sheath ◽  
Limited Capacity ◽  
C4 Species ◽  
Bundle Sheath Cells ◽  
C3 Photosynthesis ◽  
Mitochondrial Aspartate Aminotransferase ◽  
Sheath Cells

Strands of bundle sheath cells isolated from the NADP malic enzyme type C4 species, Zea mays, rapidly decarboxylate malate via NADP malic enzyme. The present studies show that these cells also decarboxylate aspartate, but at much lower rates. Aspartate decarboxylation is dependent upon added 2-oxoglutarate, is partially light dependent, and apparently proceeds via the following reaction sequence: aspartate ͛4 oxaloacetate ͛4 malate ͛4 pyruvate + CO2. Studies of the activity, properties, and location of enzymes indicated that these reactions are catalysed by a mitochondrial aspartate aminotransferase, mitochondrial or cytoplasmic NAD malate dehydrogenase, and chloroplast-located NADP malic enzyme, respectively. A mitochondria preparation isolated from Z. mays bundle sheath cells converted aspartate to oxaloacetate (with 2-oxoglutarate) and also pyruvate to alanine (with glutamate); the preparation did not reduce oxaloacetate to malate or decarboxylate malate at significant rates. Bundle sheath strands of Z. mays have a relatively limited capacity for HCO3- plus ribose 5-phosphate dependent oxygen evolution and rates were almost as high with aspartate plus 2-oxoglutarate. We suggest that amongst NADP malic enzyme type C4 species there may be a direct relationsip between the capacity of bundle sheath cells to decarboxylate aspartate and their potential for the photosystem II-mediated oxygen evolution.

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