scholarly journals Stimulation by Light of Rapid pH Regulation in the Chloroplast Stroma in Vivo as Indicated by CO2 Solubilization in Leaves

1995 ◽  
Vol 108 (3) ◽  
pp. 1059-1066 ◽  
Author(s):  
M. Hauser ◽  
H. Eichelmann ◽  
V. Oja ◽  
U. Heber ◽  
A. Laisk
Keyword(s):  
Ph Regulation ◽  
Chloroplast Stroma

Regulation of Fructose 1,6-Bisphosphatase Activity of Chlorella by Mole Mass Change

1996 ◽  
Vol 51 (9-10) ◽  
pp. 639-645 ◽  
Author(s):  
N. Grotjohann
Keyword(s):  
Enzyme Regulation ◽  
Fold Increase ◽  
Substrate Affinity ◽  
Kinetic Properties ◽  
Enzyme Form ◽  
Phosphorylated Compounds ◽  
Fructose 1,6 Bisphosphatase ◽  
Chloroplast Stroma ◽  
Fructose 1,6 Bisphosphate

Fast protein liquid chromatography on Superose 6 of partially purified FBPase II from Chlorella reveals a 1350 kDa-form at pH 6.0 and a 67 kDa-form at pH 8.5. Treatment of the large enzyme form with 5mᴍ concentrations of Mg2+, F1,6P2, DTT or ATP leads to dissociation into smaller ones of 215 -470 kDa. Aggregation/dissoziation is a reversible process, as has been shown for the effect of F1,6P2 and of pH, by rechromatography. The change in mole mass results in alterations of the activitiy and of the kinetic properties of the enzyme forms, obtained. Dissociation results in a 4 - 6 fold increase in activity, as can be shown for F1,6P2-treated samples. Halfsaturation constants, as well as the degree of cooperativity of the 67- and the 1350- kDa form, are different for substrate affinity, activation by Mg2+ and DTT, and for inhibition by ATP. Both enzyme forms hydrolyse fructose 1,6 bisphosphate and seduheptulose 1,7 bisphosphate better than other phosphorylated compounds. The ratio of F1,6P2- to SDP-cleavage is 100:58 for the small enzyme form and 100: 84 for the large one. Activation of FBPase II in the light and inactivation in the dark is discussed on the basis of different oligomeric forms of the enzyme, generated by changes in the concentration of intermediates and effectors in the chloroplast stroma, leading to dissociation or aggregation. The conclusion is drawn that oligomerization of key enzymes, resulting in enzyme forms with different activities and different kinetic properties, might provide an effective mechanism for enzyme regulation in vivo

scholarly journals A calcineurin homologous protein is required for sodium-proton exchange events in the C. elegans intestine

2011 ◽  
Vol 301 (6) ◽  
pp. C1389-C1403 ◽  
Author(s):  
Jamie Wagner ◽  
Erik Allman ◽  
Ashley Taylor ◽  
Kiri Ulmschneider ◽  
Timothy Kovanda ◽  
...  
Keyword(s):  
Muscle Contraction ◽  
Calcium Binding ◽  
Ph Regulation ◽  
Normal Animal ◽  
Motor Program ◽  
Proton Exchange ◽  
Calcium Flux ◽  
Calcium Oscillation ◽  
Homologous Proteins

Caenorhabditis elegans defecation is a rhythmic behavior, composed of three sequential muscle contractions, with a 50-s periodicity. The motor program is driven by oscillatory calcium signaling in the intestine. Proton fluxes, which require sodium-proton exchangers at the apical and basolateral intestinal membranes, parallel the intestinal calcium flux. These proton shifts are critical for defecation-associated muscle contraction, nutrient uptake, and longevity. How sodium-proton exchangers are activated in time with intestinal calcium oscillation is not known. The posterior body defecation contraction mutant ( pbo-1) encodes a calcium-binding protein with homology to calcineurin homologous proteins, which are putative cofactors for mammalian sodium-proton exchangers. Loss of pbo-1 function results in a weakened defecation muscle contraction and a caloric restriction phenotype. Both of these phenotypes also arise from dysfunctions in pH regulation due to mutations in intestinal sodium-proton exchangers. Dynamic, in vivo imaging of intestinal proton flux in pbo-1 mutants using genetically encoded pH biosensors demonstrates that proton movements associated with these sodium-proton exchangers are significantly reduced. The basolateral acidification that signals the first defecation motor contraction is scant in the mutant compared with a normal animal. Luminal and cytoplasmic pH shifts are much reduced in the absence of PBO-1 compared with control animals. We conclude that pbo-1 is required for normal sodium-proton exchanger activity and may couple calcium and proton signaling events.

scholarly journals Intracellular pH distribution as a cell health indicator in Saccharomyces cerevisiae

2011 ◽  
Vol 8 (64) ◽  
pp. 1635-1643 ◽  
Author(s):  
Thomas Aabo ◽  
Jesper Glückstad ◽  
Henrik Siegumfeldt ◽  
Nils Arneborg
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Intracellular Ph ◽  
Ph Regulation ◽  
Metabolic Enzyme ◽  
Transport Mechanisms ◽  
Cell Functions ◽  
Internal Ph ◽  
Ratio Imaging

Internal pH regulation is vital for many cell functions, including transport mechanisms and metabolic enzyme activity. More specifically, transport mechanisms are to a wide degree governed by internal pH distributions. We introduce the term standard deviation of the intracellular pH (s.d.(pH int )) to describe the internal pH distributions. The cellular pH distributional response to external stress such as heat has not previously been determined. In this study, the intracellular pH (pH i ) and the s.d.(pH int ) of Saccharomyces cerevisiae cells exposed to supralethal temperatures were measured using fluorescence ratio imaging microscopy (FRIM). An exponential decline in pH i was observed after an initial small decline. For the first time, we report the use of FRIM for determining in vivo plasma membrane proton permeability coefficients in yeast. Furthermore, the exponential decay of pH i and the rupture of the cell plasma membrane, as measured by propidium iodide staining, at 70°C were not simultaneous but were separated by a significant temporal difference. Finally, a nonlinear relationship between the pH i and s.d.(pH int ) was found; i.e. the s.d.(pH int ) was significantly more sensitive to supralethal temperatures than pH i . s.d.(pH int ) is therefore proposed as an early health/vitality indicator in S. cerevisiae cells exposed to heat stress.

scholarly journals Properties of freshly purified and thiol-treated spinach chloroplast fructose bisphosphatase

1980 ◽  
Vol 185 (3) ◽  
pp. 689-693 ◽  
Author(s):  
S A Charles ◽  
B Halliwell
Keyword(s):  
Inorganic Phosphate ◽  
Physiological Significance ◽  
Fructose Bisphosphatase ◽  
Spinach Chloroplast ◽  
Significant Rate ◽  
Chloroplast Stroma ◽  
Fructose 1,6 Bisphosphate

Freshly purified spinach chloroplast fructose bisphosphatase is powerfully inhibited by inorganic phosphate competitively with respect to its substrate fructose 1,6-bisphosphate. The concentrations of phosphate and substrate in the chloroplast stroma are such that the enzyme in this form could not operate at a significant rate in vivo. Incubation of the enzyme with dithiothreitol for 24 h decreases the Km for fructose 1,6-bisphosphate from 0.8 to 0.033 mM, decreases the Km for Mg2+ from 9 to 2 mM and substantially alleviates inhibition by inorganic phosphate. The physiological significance of thiol activation of the enzyme is discussed.

scholarly journals Temperature-dependent pH regulation in stenothermal Antarctic and eurythermal temperate eelpout (Zoarcidae): an in-vivo NMR study

Polar Biology ◽  
2001 ◽  
Vol 24 (11) ◽  
pp. 869-874 ◽  
Author(s):  
Christian Bock ◽  
Franz Sartoris ◽  
Wittig Rolf-M. ◽  
Pörtner Hans-O.
Keyword(s):  
Ph Regulation ◽  
Temperature Dependent ◽  
In Vivo Nmr ◽  
Nmr Study

scholarly journals pH Regulation of Pectate Lyase Secretion Modulates the Attack of Colletotrichum gloeosporioides on Avocado Fruits

2000 ◽  
Vol 66 (3) ◽  
pp. 1026-1030 ◽  
Author(s):  
Nir Yakoby ◽  
Ilana Kobiler ◽  
Amos Dinoor ◽  
Dov Prusky
Keyword(s):  
Protein Secretion ◽  
Colletotrichum Gloeosporioides ◽  
Ph Regulation ◽  
Pectate Lyase ◽  
Persea Americana ◽  
Postharvest Diseases ◽  
New Approaches ◽  
Pectolytic Enzyme

ABSTRACT Growth of Colletotrichum gloeosporioides in pectolytic enzyme-inducing medium (PEIM) increased the pH of the medium from 3.8 to 6.5. Pectate lyase (PL) secretion was detected when the pH reached 5.8, and the level of secretion increased up to pH 6.5. PL gene (pel) transcript production began at pH 5.0 and increased up to pH 5.7. PL secretion was never detected when the pH of the inducing medium was lower than 5.8 or when C. gloeosporioides hyphae were transferred from PL-secreting conditions at pH 6.5 to pH 3.8. This behavior differed from that of polygalacturonase (PG), where pg transcripts and protein secretion were detected at pH 5.0 and continued up to 5.7. Under in vivo conditions, the pH of unripe pericarp of freshly harvested avocado (Persea americana cv. Fuerte) fruits, resistant to C. gloeosporioides attack, was 5.2, whereas in ripe fruits, when decay symptoms were expressed, the pericarp pH had increased to 6.3. Two avocado cultivars, Ardit and Ettinger, which are resistant toC. gloeosporioides attack, had pericarp pHs of less than 5.5, which did not increase during ripening. The present results suggest that host pH regulates the secretion of PL and may affectC. gloeosporioides pathogenicity. The mechanism found in avocado may have equivalents in other postharvest pathosystems and suggests new approaches for breeding against and controlling postharvest diseases.

The carbonic anhydrase gene families of Chlamydomonas reinhardtii

2005 ◽  
Vol 83 (7) ◽  
pp. 780-795 ◽  
Author(s):  
Mautusi Mitra ◽  
Catherine B Mason ◽  
Ying Xiao ◽  
Ruby A Ynalvez ◽  
Scott M Lato ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Gene Families ◽  
Carbonic Anhydrases ◽  
Photosynthetic Organisms ◽  
Surrounding Environment ◽  
Concentrating Mechanism ◽  
Chloroplast Stroma ◽  
Carbonic Anhydrase Gene

Carbonic anhydrases (CAs) are zinc-containing metalloenzymes that catalyze the reversible interconversion of CO2 and HCO3–. Aquatic photosynthetic organisms have evolved different forms of CO2-concentrating mechanisms to aid Rubisco in capturing CO2 from the surrounding environment. One aspect of all CO2-concentrating mechanisms is the critical roles played by various specially localized extracellular and intracellular CAs. There are three evolutionarily unrelated CA families designated α-, β-, and γ-CA. In the green alga, Chlamydomonas reinhardtii Dangeard, eight CAs have now been identified, including three α-CAs and five β-CAs. In addition, C. reinhardtii has another CA-like gene, Glp1 that is similar to known γ-CAs. To characterize these different CA isoforms, some of the CA genes have been overexpressed to determine whether the proteins have CA activity and to generate antibodies for in vivo immunolocalization. The CA proteins Cah3, Cah6, and Cah8, and the γ-CA-like protein, Glp1, have been overexpressed. Cah3, Cah6, and Cah8 have CA activity, but Glp1 does not. At least two of these proteins, Cah3 and Cah6, are localized to the chloroplast. Using immunolocalization and sequence analyses, we have determined that Cah6 is located to the chloroplast stroma and confirmed that Cah3 is localized to the chloroplast thylakoid lumen. Activity assays show that Cah3 is 100 times more sensitive to sulfonamides than Cah6. We present a model on how these two chloroplast CAs might participate in the CO2-concentrating mechanism of C. reinhardtii. Key words: carbonic anhydrase, CO2-concentrating mechanism, Chlamydomonas, immunolocalization.

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