scholarly journals Land plant biochemistry

2000 ◽  
Vol 355 (1398) ◽  
pp. 833-846 ◽  
Author(s):  
J. A. Raven
Keyword(s):  
Large Subunit ◽  
Molecular Genetic ◽  
Land Plant ◽  
Water Repellent ◽  
Ribulose Bisphosphate Carboxylase ◽  
Bisphosphate Carboxylase ◽  
Plant Biochemistry ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Molecular Phylogenetic ◽  
Molecular Genetic Evidence

Biochemical studies have complemented ultrastructural and, subsequently, molecular genetic evidence consistent with the Charophyceae being the closest extant algal relatives of the embryophytes. Among the genes used in such molecular phylogenetic studies is that ( rbcL ) for the large subunit of ribulose bisphosphate carboxylase–oxygenase (RUBISCO). The RUBISCO of the embryophytes is derived, via the Chlorophyta, from that of the cyanobacteria. This clade of the molecular phylogeny of RUBISCO shows a range of kinetic characteristics, especially of CO 2 affinities and of CO 2 / O 2 selectivities. The range of these kinetic values within the bryophytes is no greater than in the rest of the embryophytes; this has implications for the evolution of the embryophytes in the high atmospheric CO 2 environment of the late Lower Palaeozoic. The differences in biochemistry between charophycean algae and embryophytes can to some extent be related functionally to the structure and physiology of embryophytes. Examples of components of embryophytes, which are qualitatively or quantitatively different from those of charophytes, are the water repellent/water resistant extracellular lipids, the rigid phenolic polymers functional in waterconducting elements and mechanical support in air, and in UV–B absorption, flavonoid phenolics involved in UV–B absorption and in interactions with other organisms, and the greater emphasis on low M r organic acids, retained in the plant as free acids or salts, or secreted to the rhizosphere. The roles of these components are discussed in relation to the environmental conditions at the time of evolution of the terrestrial embryophytes. A significant point about embryophytes is the predominance of nitrogen–free extracellular structural material (a trait shared by most algae) and UV–B screening components, by contrast with analogous components in many other organisms. An important question, which has thus far been incompletely addressed, is the extent to which the absence from bryophytes of the biochemical pathways which produce components found only in tracheophytes is the result of evolutionary loss of these functions.

scholarly journals Effect of mutation of lysine-128 of the large subunit of ribulose bisphosphate carboxylase/oxygenase from Anacystis nidulans

1998 ◽  
Vol 336 (2) ◽  
pp. 387-393 ◽  
Author(s):  
Graeme BAINBRIDGE ◽  
P. John ANRALOJC ◽  
Pippa J. MADGWICK ◽  
Jim E. PITTS ◽  
Martin A. J. PARRY
Keyword(s):  
Aspartic Acid ◽  
Active Site ◽  
Large Subunit ◽  
Ribulose Bisphosphate Carboxylase ◽  
Bisphosphate Carboxylase ◽  
Catalytic Function ◽  
Loop Dynamics ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Genes Encoding ◽  
Specificity Factor

The contribution of lysine-128 within the active site of Anacystis nidulansd-ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) was investigated by the characterization of mutants in which lysine-128 was replaced with arginine, glycine, glutamine, histidine or aspartic acid. Mutated genes encoding the Rubisco large subunit were expressed in Escherichia coliand the resultant polypeptides assembled into active complexes. All of the mutant enzymes had a lower affinity for ribulose 1,5-bisphosphate (RuBP) and lower rates of carboxylation. Substitution of lysine-128 with glutamine, histidine or aspartic acid decreased the specificity factor and led to the production of an additional monophosphate reaction product. We show that this product results from the loss of the phosphate from C-1 of RuBP, most probably by β-elimination from the 2,3-enediolate derivative of RuBP. The results confirm that lysine-128 is important in determining the position of the essential ε-amino group of lysine-334 within the active site and in loop dynamics. This further demonstrates that residues remote from the active site can be manipulated to modify catalytic function.

The CO2/O2 specificity of single-subunit ribulose-bisphosphate carboxylase from the dinoflagellate, Amphidinium carterae

1998 ◽  
Vol 25 (2) ◽  
pp. 131 ◽  
Author(s):  
Spencer M. Whitney ◽  
T. John Andrews
Keyword(s):  
Large Subunit ◽  
Anaerobic Bacteria ◽  
Carbon Gain ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Amphidinium Carterae ◽  
Bisphosphate Carboxylase ◽  
Cell Extracts ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Alternate Substrate

Some dinoflagellates have been shown recently to be unique among eukaryotes in having a ribulose-bisphosphate carboxylase-oxygenase (Rubisco, EC 4.1.1.39) composed of only one type of subunit, the 53-kDa large subunit [reviewed by Palmer, J.D. (1996) Plant Cell 8, 343–345]. Formerly, such homomeric Rubiscos had been found only in anaerobic bacteria and are characterised by such poor abilities to discriminate against the competitive alternate substrate, O2, that they would not be able to support net carbon gain if exposed to the current atmospheric CO2/O2 ratio. The capacity of Rubiscos from aerobic organisms to discriminate more effectively against O2 appeared to correlate with the presence of additional 12- to 18-kDa small subunits. Thus the CO2/O2 specificity of the homomeric dinoflagellate Rubisco is of considerable interest from the structural, physiological and evolutionary viewpoints. However, for unknown reasons, Rubiscos from dinoflagellates studied so far are so unstable after extraction from the cells that kinetic characterisation has not been possible. We redesigned two methods for measuring Rubisco’s CO2/O2 specificity to adapt them to rapid measurement at 10°C using unfractionated cell extracts. Both methods revealed that the CO2/O2 specificity of Rubisco from the dinoflagellate, Amphidinium carterae Hulburt, was approximately twice as great as that of other homomeric Rubiscos but unlikely to be sufficient to support dinoflagellate photosynthesis without assistance from an inorganic-carbon-concentrating mechanism.

Changes in the net charge and subunit properties of ribulose bisphosphate carboxylase–oxygenase during cold hardening of Puma rye

1979 ◽  
Vol 57 (2) ◽  
pp. 155-164 ◽  
Author(s):  
N. P. A. Huner ◽  
F. D. H. Macdowall
Keyword(s):  
Molecular Weight ◽  
Large Subunit ◽  
Sodium Dodecyl ◽  
Reducing Agent ◽  
Cold Hardening ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Thaw Cycle ◽  
Ribulose Bisphosphate Carboxylase Oxygenase

Ribulose bisphosphate carboxylase–oxygenase (RUBPCase) from leaves of cold-hardened and unhardened Puma rye was purified by gel filtration and ion exchange chromatography. The specific activity of the hardened form was twice that of the unhardened form. A difference in charge between the two forms of this enzyme was proved by gel electrofocussing. The estimated isoelectric point (pI) values were 6.4 and 6.3 for the enzyme from the hardened and unhardened source respectively. The large subunit (55 000 molecular weight) of the enzyme from only the unhardened source formed an apparent dimer during sodium dodecyl sulfate (SDS) gel electrophoresis. At pH 6.8 it was also the source of an anomalous polypeptide with an apparent molecular weight of 47 000. This anomalous polypeptide appeared in both hardened and unhardened preparations after irreversible inactivation of RUBPCase activity by NaCl. It also appeared after preparation of the purified enzymes for SDS–PAGE in the absence of β-mercaptoethanol, but this was reversible. The enzyme from the hardened source was less affected in the absence of reducing agent. Structural evidence was obtained for the previously reported cold hardening of the enzyme against freeze inactivation. A freeze–thaw cycle applied to the enzyme in vitro caused some polymerization of the large subunit and its anomalous polypeptide, in the absence of reducing agent, especially in the unhardened case. This increased with repeated cycles until the fifth cycle when the large subunit monomer and its satellite were abolished only in preparations from the unhardened source. These data indicate that the large subunit is a probable site of change that occurred in this enzyme during cold hardening.

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