SOME OBSERVATIONS ON THE FORMATION OF GLYCERIC ACID DURING PHOTOSYNTHESIS EXPERIMENTS

1961 ◽  
Vol 39 (1) ◽  
pp. 1-5 ◽  
Author(s):  
D. C. Mortimer
Keyword(s):  
Enzymatic Activity ◽  
Glyceric Acid ◽  
Short Term ◽  
Alternate Pathway ◽  
Phosphoglyceric Acid ◽  
Soybean Leaf ◽  
Photosynthetic Assimilation ◽  
Hydrolysis Of

The dephosphorylation of phosphoglyceric acid was tested under a variety of conditions. Hydrolysis of the ester by leaf homogenates was relatively slow, even when conditions favored enzymatic activity, and was not detected when frozen homogenate was extracted by boiling 80% ethanol. The results suggest that glyceric acid recovered in ethanol-soluble extracts of leaves following short-term photosynthesis experiments is not normally derived from phosphoglyceric acid. The route proposed for the synthesis of glyceric acid is related, with particular reference to soybean leaf, to an alternate pathway for photosynthetic assimilation which does not utilize phosphoglyceric acid.

THE INCORPORATION OF C14 INTO CELLULOSE AND OTHER POLYSACCHARIDES OF SUGAR BEET LEAF DURING SHORT TERM PHOTOSYNTHESIS IN C14O2

1962 ◽  
Vol 40 (1) ◽  
pp. 1-11 ◽  
Author(s):  
D. C. Mortimer ◽  
Clare B. Wylam
Keyword(s):  
Carbon Dioxide ◽  
Sugar Beet ◽  
Potassium Hydroxide ◽  
Soluble Fraction ◽  
Short Term ◽  
Photosynthetic Assimilation ◽  
To Receive ◽  
Hydrolysis Of ◽  
Soluble Fractions

The carbohydrates of sugar beet leaf were fractionated by successive extractions in ethanol, water, and three concentrations of potassium hydroxide. Quantitative hydrolysis of the polysaccharides from the water- and alkali-soluble fractions gave galactose, glucose, arabinose, xylose, ribose, and rhamnose in varying proportions. When these fractions from leaves which had photosynthetically assimilated C14O2 for 10 to 120 seconds were analyzed, all fractions, including the alkali-insoluble cellulose, were labelled after only 10 seconds. The proportion of C14 in the alkali-soluble fraction was high relative to that in cellulose after 10 seconds, but similar in both fractions after longer periods. All of the radioactivity in the carbohydrates was in glucose (apart from the fructose of sucrose). When photosynthesis in C14O2 was followed by photosynthetic periods in normal air, the polysaccharide fractions all continued to receive C14-labelled glucose for about 5 minutes. No significant transfer of radioactivity from one fraction to another was detected during an additional 40 minutes. The data indicate that the formation of leaf polysaccharides is closely linked to early products of the photosynthetic assimilation of carbon dioxide, and that the different polysaccharides are formed concurrently with little interconversion.

The enzymatic activity of phosphoglycerate mutase from gram-positive endospore-forming bacteria requires Mn2+ and is pH sensitive

1998 ◽  
Vol 44 (8) ◽  
pp. 759-767 ◽  
Author(s):  
Monica Chander ◽  
Barbara Setlow ◽  
Peter Setlow
Keyword(s):  
Enzymatic Activity ◽  
Micrococcus Luteus ◽  
Streptomyces Coelicolor ◽  
Ph Sensitive ◽  
Phosphoglycerate Mutase ◽  
Glyceric Acid ◽  
Ph Change ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Phosphoglyceric Acid

The enzymatic activity of phosphoglycerate mutase (Pgm) from three gram-positive endospore-forming bacteria (Bacillus subtilis, Clostridium perfringens, and Sporosarcina ureae) requires Mn2+ and is very sensitive to pH; at low concentrations of Mn2+, a pH change from 8 to 6 resulted in greater than 30- to 200-fold decreases in the activity of these Pgms. However, Pgm deactivation at pH 6 was reversed by shifting the enzyme to pH 7 or 8. Free Mn2+ was not directly involved in Pgm catalysis, although enzyme-bound Mn2+ may be involved. The rate of catalysis by Mn2+-containing Pgm was also slightly pH dependent, although the Km for 3-phosphoglyceric acid appeared to be the same at pH 6, 7, and 8. These findings suggest that Mn2+ binds to catalytically inactive Pgm and converts it to a catalytically competent form, and further, that pH influences the efficiency with which the enzyme binds Mn2+. The extreme pH sensitivity of the Mn2+-dependent Pgms supports a model in which this enzyme is inhibited during sporulation by acidification of the forespore, thus allowing accumulation of the spore's large depot of 3-phospho-glyceric acid. The activity of Pgm from two closely related gram-positive bacteria that do not form spores (Planococcus citreus and Staphylococcus saprophyticus) also requires Mn2+ and is pH sensitive. In contrast, the Pgm activities from two more distantly related non-endospore-forming gram-positive bacteria (Micrococcus luteus and Streptomyces coelicolor) are neither dependent on metal ions nor particularly sensitive to pH.Key words: Bacillus, Clostridium, Mn2+, phosphoglycerate mutase, sporulation.

SOME SHORT-TERM EFFECTS OF INCREASED CARBON DIOXIDE CONCENTRATION ON PHOTOSYNTHETIC ASSIMILATION IN LEAVES

1959 ◽  
Vol 37 (6) ◽  
pp. 1191-1201 ◽  
Author(s):  
D. C. Mortimer
Keyword(s):  
Carbon Dioxide ◽  
Plant Species ◽  
Closed System ◽  
Carbon Dioxide Concentration ◽  
Experimental Period ◽  
Glyceric Acid ◽  
Short Term ◽  
Radioactive Carbon ◽  
Photosynthetic Assimilation ◽  
Atmospheric Level

The photosynthetic assimilation of radioactive carbon dioxide by leaves from seven plant species was continuously measured in a closed system in which the concentration of carbon dioxide was abruptly increased from the atmospheric level to predetermined levels up to 2.0%. The rate of assimilation immediately increased, approximately proportional to concentration, but after about one minute began to decrease. The degree and duration of the decrease in rate of uptake varied with plant species and with concentration. This increased uptake of carbon dioxide influenced the distribution of carbon among the products of assimilation. At the lowest concentration (0.1%), serine, glycine, and glyceric acid contained most of the carbon assimilated during the experimental period, but at higher concentrations these were replaced by sucrose and alanine.

IODOACETATE INHIBITION OF PHOTOSYNTHETIC CARBON DIOXIDE ASSIMILATION IN SUGAR BEET AND SOYBEAN LEAVES

1960 ◽  
Vol 38 (4) ◽  
pp. 623-634 ◽  
Author(s):  
D. C. Mortimer
Keyword(s):  
Carbon Dioxide ◽  
Sugar Beet ◽  
Aspartic Acid ◽  
Glyceric Acid ◽  
Carbon Dioxide Assimilation ◽  
Alternate Pathway ◽  
Acid Incorporation ◽  
Photosynthetic Carbon ◽  
Phosphoglyceric Acid ◽  
Soybean Leaves

When the petioles of freshly excised sugar beet or soybean leaves were immersed in dilute iodoacetate solutions, the rates of photosynthetic carbon dioxide assimilation were reduced and characteristic changes in the distribution of assimilated C14 were observed. Inhibited sugar beet leaves accumulated C14 in phosphoglyceric acid (PGA) and aspartic acid, but did not incorporate C14 into glyceric acid. Inhibited soybean leaves continued to form glyceric acid, but did not incorporate C14 into PGA and only trace amounts into aspartic acid. Incorporation of C14 into sucrose by the sugar beet leaf ceased when the assimilation of carbon dioxide was reduced below 1/10th of normal, while soybean leaves still formed sucrose at that level of inhibition. It was concluded from these and other data that the mechanisms for photosynthetic carbon dioxide assimilation in the two species were different. The iodoacetate-sensitive, PGA-glyceraldehyde-3-phosphate reduction, which could account for only part of the assimilation by sugar beet leaves, did not appear to be utilized by soybean leaves. An alternate pathway for the reduction of carbon dioxide to the carbohydrate level is postulated to account for the assimilation patterns observed in the two species.

Urea hydrolysis and inorganic N in a Luvisol after application of fertiliser containing rare-earth elements

Soil Research ◽  
2003 ◽  
Vol 41 (4) ◽  
pp. 741 ◽  
Author(s):  
Xingkai Xu ◽  
Zijian Wang ◽  
Yuesi Wang ◽  
Kazuyuki Inubushi
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Substantial Reduction ◽  
Application Rate ◽  
Urea Hydrolysis ◽  
High Rate ◽  
Short Term ◽  
N Content ◽  
N Fertilisers ◽  
Hydrolysis Of

In recent decades, Chinese agriculturists have used rare-earth-containing fertilisers as basal fertilisers together with N fertilisers (e.g. urea). We studied urea hydrolysis and its hydrolysis products in a laboratory experiment using urea-N fertiliser with rare earths at rates from 0.5 to 50% (w/w). The results indicated that application of rare earths at a high rate could result in a short-term inhibition of urea hydrolysis and an increase in soil (NH4+ + NO3– + NO2–)-N content. When the application rate of rare earths was higher than 5% of the applied urea-N (corresponding to 10 mg/kg soil), soil exchangeable NH4+-N content increased significantly following the hydrolysis of the applied urea. Increasing the application rate of rare earths appeared to reduce the content of soil urea-derived (NO3– + NO2–)-N. A substantial reduction in soil pH was found immediately after application of rare earths and urea. We conclude that application of rare earths at >10 mg/kg may lead to a substantial increase in the content of urea-derived N in the soil, via the inhibition of urea hydrolysis and nitrification.

Colorimetric Screening Device for Pesticide Analysis Based on the Liposome

2013 ◽  
Vol 726-731 ◽  
pp. 850-853
Author(s):  
Hua Nan Guan
Keyword(s):  
Enzymatic Activity ◽  
Organophosphorus Pesticides ◽  
Ph Sensitive ◽  
Pesticide Analysis ◽  
Ph Indicator ◽  
Fluorescent Indicator ◽  
Fluorescent Signal ◽  
Low Levels ◽  
Screening Device ◽  
Hydrolysis Of

Monitoring of the organophosphorus pesticides dichlorvos at very low levels has been achieved with liposome-based nanobiosensors. The enzyme acetylcholinesterase was effectively stabilized within the internal nanoenvironment of the liposomes. Within the liposomes, the pH sensitive fluorescent indicator pyranine was also immobilized for the optical transduction of the enzymatic activity. Increasing amounts of pesticides lead to the decrease of the enzymatic activity for the hydrolysis of the acetylcholine and thus to a decrease in the fluorescent signal of the pH indicator. The decrease of the liposome biosensors signal is relative to the concentration of dichlorvos down to 10-12 M levels. Also a colorimetric screening device for pesticide analysis has been evaluated.

scholarly journals Kinetic probes for inter-domain co-operation in human somatic angiotensin-converting enzyme

2005 ◽  
Vol 391 (3) ◽  
pp. 641-647 ◽  
Author(s):  
Olga E. Skirgello ◽  
Peter V. Binevski ◽  
Vladimir F. Pozdnev ◽  
Olga A. Kost
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Enzymatic Activity ◽  
Active Site ◽  
The Other ◽  
Converting Enzyme ◽  
Human Enzyme ◽  
Independent Functions ◽  
The Common ◽  
The Individual ◽  
Hydrolysis Of

s-ACE (the somatic form of angiotensin-converting enzyme) consists of two homologous domains (N- and C-domains), each bearing a catalytic site. Negative co-operativity between the two domains has been demonstrated for cow and pig ACEs. However, for the human enzyme there are conflicting reports in the literature: some suggest possible negative co-operativity between the domains, whereas others indicate independent functions of the domains within s-ACE. We demonstrate here that a 1:1 stoichiometry for the binding of the common ACE inhibitors, captopril and lisinopril, to human s-ACE is enough to abolish enzymatic activity towards FA {N-[3-(2-furyl)acryloyl]}-Phe-GlyGly, Cbz (benzyloxycarbonyl)-Phe-His-Leu or Hip (N-benzoylglycyl)-His-Leu. The kinetic parameters for the hydrolysis of seven tripeptide substrates by human s-ACE appeared to represent average values for parameters obtained for the individual N- and C-domains. Kinetic analysis of the simultaneous hydrolysis of two substrates, Hip-His-Leu (S1) and Cbz-Phe-His-Leu (S2), with a common product (His-Leu) by s-ACE at different values for the ratio of the initial concentrations of these substrates (i.e. σ=[S2]0/[S1]0) demonstrated competition of these substrates for binding to the s-ACE molecule, i.e. binding of a substrate at one active site makes the other site unavailable for either the same or a different substrate. Thus the two domains within human s-ACE exhibit strong negative co-operativity upon binding of common inhibitors and in the hydrolysis reactions of tripeptide substrates.

Simple and Rapid Determination of Phytase Activity

1994 ◽  
Vol 77 (3) ◽  
pp. 760-764 ◽  
Author(s):  
Adrianus J Engelen ◽  
Fred C Van Der Heeft ◽  
Peter H G Randsdorp ◽  
Ed L C Smtt
Keyword(s):  
Enzymatic Activity ◽  
Rapid Method ◽  
Rapid Determination ◽  
Phytase Activity ◽  
Sodium Phytate ◽  
Microbial Phytase ◽  
Hydrolysis Of

Abstract A simple and rapid method is described for determining the enzymatic activity of microbial phytase. The method is based on the determination of inorganic orthophosphate released on hydrolysis of sodium phytate at pH 5.5.

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