Assessing the Degree of C4 Photosynthesis in C3-C4 Species Using an Inhibitor of Phosphoenolpyruvate Carboxylase

The stability of phosphoenolpyruvate carboxylase (EC 4.1.1.31) was examined following extraction of the enzyme from leaves of several C4 plants. Extracts were rapidly processed on small Sephadex G-25 columns to free protein of small-molecular-weight compounds. With most of the species examined, activity was rapidly lost at both 0 and 25°C when the pH was about 7.8 or higher. Addition of bovine serum albumin to extracts incubated at 25°C and pH 8.2 not only prevented inactivation with several species, but resulted in a substantial increase in activity. The addition of dithiothreitol plus Mg2+ to extracts from some of these species reduced or prevented inactivation. With extracts maintained at 0°C, addition of either bovine serum albumin or dithiothreitol was effective only in reducing the rate of inactivation in extracts. Phosphoenolpyruvate carboxylase activity remained stable, or increased substantially, when extracts buffered between pH 7.4 and 6.9 were incubated at either 0 or 25°C. Activation was usually complete within an hour and was often significantly greater at 25°C or when bovine serum albumin was added. The activity of partially purified phosphoenolpyruvate carboxylase from Zea mays was similarly affected by pH, temperature, and bovine serum albumin. The present studies raise doubts about the accuracy of phosphoenolpyruvate carboxylase determinations made during the course of some previous studies on C4 species. Reliable procedures for the determination of phosphoenolpyruvate carboxylase activity in C4 plant extracts are described. Possible physiological implications of the results are considered.

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Coordinate Regulation of Phosphoenolpyruvate Carboxylase and Phosphoenolpyruvate Carboxykinase by Light and CO2 during C4 Photosynthesis

PLANT PHYSIOLOGY ◽

10.1104/pp.106.093013 ◽

2007 ◽

Vol 144 (1) ◽

pp. 479-486 ◽

Cited By ~ 29

Author(s):

Karen J. Bailey ◽

Julie E. Gray ◽

Robert P. Walker ◽

Richard C. Leegood

Keyword(s):

Phosphoenolpyruvate Carboxylase ◽

Phosphoenolpyruvate Carboxykinase ◽

C4 Photosynthesis ◽

Coordinate Regulation

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Mapping of Non-methylated and Methylated Restriction Sites in the Promoter Region of the Maize Gene for Phosphoenolpyruvate Carboxylase Involved in C4 Photosynthesis.

Agricultural and Biological Chemistry ◽

10.1271/bbb1961.55.2877 ◽

1991 ◽

Vol 55 (11) ◽

pp. 2877-2879

Author(s):

Shuichi YANAGISAWA ◽

Yasuo MORI ◽

Takao KAWAMURA ◽

Katsura Izui

Keyword(s):

Phosphoenolpyruvate Carboxylase ◽

Promoter Region ◽

C4 Photosynthesis ◽

Restriction Sites ◽

Maize Gene

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Photosynthetic Mechanisms of Weeds in Taiwan

Functional Plant Biology ◽

10.1071/pp9930757 ◽

1993 ◽

Vol 20 (6) ◽

pp. 757 ◽

Cited By ~ 8

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.

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