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U Matern

Publications and source records attributed to U Matern.

71 records · Page 4Linked to original sources
PubMed1983

Acylhydrolases from parsley (Petroselinum hortense). Relative distribution and properties of four esterases hydrolyzing malonic acid hemiesters of flavonoid glucosides.

In parsley, malonylated flavonoid glycosides are formed in response to ultraviolet irradiation and accumulate in the vacuoles. Involvement of malonyltransferases, which catalyze the transfer of malonic acid from malonyl-coenzyme A to either flavone/flavonol 7-O-glucosides or flavonol 3-O-glucosides, has been described previously. These enzymes are present in very young leaf buds, and their activities decrease rapidly when leaves begin to unfold, while at the same time esterase activity is developing. The latter enzyme activity continues to increase with tissue age. Four esterases, distinguished by pI's of 3.8, 3.9, 4.0, and 4.05, were purified to apparent homogeneity from parsley leaves and shown to hydrolyze malonic acid hemiesters of flavonoid glucosides. These esterases are unspecific and are best described as one acetyl- and three arylesterases on the basis of inhibition studies by 4-chloromercuribenzoic acid and diisopropyl fluorophosphate. Esterases and malonic acid hemiesters appear to be separated from each other within the parsley leaf cell, and only on disruption of the cells do the respective substrates become available to the enzymes. Involvement of esterases in formation of wound periderm in parsley plants is suggested.

Acyltransferases↗
PubMed1983

Conformational changes of apigenin 7-O-(6-O-malonylglucoside), a vacuolar pigment from parsley, with solvent composition and proton concentration.

Malonylated apigenin 7-O-glucoside was prepared from malonyl-CoA and apigenin 7-O-glucoside using a malonyltransferase from parsley cell cultures. The enzyme product, as well as the flavonoid substrate, was analyzed by high-resolution nuclear magnetic resonance spectroscopy, confirming that malonic acid had been attached to the primary hydroxyl of the glucose moiety of apigenin 7-O-glucoside. During these studies in several solvents, it became apparent that, in particular, the chemical shift of H-6" A and the coupling constants J5",6"A and J5",6"B were dependent on solvent composition and proton concentration. Similar changes of sugar proton resonance frequencies were also observed with methyl 6-O-malonyl-beta-D-glucopyranoside, but not with apigenin 7-O-[6-O-(4-coumaroyl)glucoside]. The change of coupling constants is ascribed to a conformational modification of the sugar portion in the malonylglucosides. Malonylated flavonoid glycosides are exclusively located within the vacuoles of parsley cells. We propose that acylation of flavonoid glycosides which are synthesized in the cytoplasm facilitates transport of the substrates into the vacuole. The conformational modification which is induced by changes in proton concentration may provide a mechanism to trap flavonoids in situ.

Apigenin↗
PubMed1983

Differential response of cultured parsley cells to elicitors from two non-pathogenic strains of fungi. 1. Identification of induced products as coumarin derivatives.

Dark-grown cell suspension cultures of parsley, Petroselinum hortense, produce furanocoumarins after treatment with elicitor preparations of either Phytophthora megasperma f.sp. glycinea (Pmg elicitor) or Alternaria carthami Chowdhury (Ac elicitor). The linear furanocoumarins, psoralen and xanthotoxin, and the benzodipyrandione, graveolone, are the major products synthesized in response to Pmg elicitor, besides small amounts of the furanocoumarin bergapten. Treatment with Ac elicitor induces predominantly the formation of bergapten and the furanocoumarin isopimpinellin, as well as small amounts of graveolone. While Pmg elicitor leads to cell death within a few days, cell mass increased for at least 6 days after treatment with Ac elicitor. Brefeldin A, a phytotoxin produced by A. carthami, inhibits growth of parsley cell suspension cultures considerably at a concentration of 0.01 mM and growth of the cells ceased at a concentration of 0.1 mM toxin. Concomitantly, furanocoumarin biosynthesis was suppressed in our system by a concentration of brefeldin A within 0.01-0.1 mM.

Alternaria↗
PubMed1983

Differential response of cultured parsley cells to elicitors from two non-pathogenic strains of fungi. 2. Effects on enzyme activities.

Parsley cell cultures produce linear furanocoumarins and the linear benzodipyrandione, graveolone, in response to treatment with an elicitor from either Phytophthora megasperma or Alternaria carthami. Activities of enzymes involved in general phenylpropanoid metabolism, phenylalanine ammonia-lyase and 4-coumarate: CoA ligase, as well as of an enzyme involved specifically in furanocoumarin biosynthesis, dimethylallyl diphosphate: umbelliferone dimethylallyltransferase, were monitored over several days after treatment with A. carthami elicitor. In addition, the activities of chalcone synthase, an enzyme involved in flavonoid formation, and of glucose-6-phosphate: NADP 1-oxidoreductase were also monitored. The lyase and the ligase activities increased steadily for 48 h and the dimethylallyltransferase activity for 54 h, while the synthase activity was not altered and the oxidoreductase activity decreased gradually. In some experiments, phenylalanine ammonia-lyase activity reached a maximum value of 250 mukat/kg, twice the maximal activity observed previously in parsley cells after treatment with either ultraviolet light or an elicitor preparation from P. megasperma. In crude extracts, phenylalanine ammonia-lyase activity was shown to be inhibited by unidentified small-molecular-weight compounds which were formed in proportion to the elicitor treatment. While phenylalanine ammonia-lyase and dimethylallyl diphosphate: umbelliferone dimethylallyltransferase are known to be required for furanocoumarin biosynthesis, the involvement of 4-coumarate: CoA ligase is as yet unclear. The concomitant increase and decrease of the ligase activity with the activities of the lyase and the dimethylallyltransferase, as well as its similar response to elicitor concentrations, suggest that CoA esters of cinnamic acids play a role in the biosynthesis of furanocoumarins.

Alternaria↗
PubMed1980

mRNA-dependent regulation of UDP-apiose synthase activity in irradiated plant cells.

Large changes in the rate of synthesis of UDP-apiose synthase, an enzyme of the flavonoid glycoside pathway, were observed both in vivo and in vitro following irradiation of previously dark-grown cell suspension cultures of parsley (Petroselinum hortense). Irradiation of the cells with ultraviolet light for 2 1/2 h caused a large increase in UDP-adipose synthase mRNA activity which continued for several hours during the subsequent dark period. A sharp peak in this activity was followed by a rapid exponential decline. The timing of changes in mRNA activity was very similar for UDP-apiose synthase and chalcone synthase, a previously investigated enzyme of the flavonoid glycoside pathway, but differed from that for phenylalanine ammonia-lyase, an enzyme of general phenylpropanoid metabolism. Thus, the present data provide further evidence for a differential regulation of the two groups of enzymes and a high degree of co-ordination within each group. The expected light-induced changes in UDP-apiose synthase activity were calculated from the observed changes in the rate of synthesis, allowing for an apparently constant rate of degradation (t 1/2 = 17 h). The resulting time course was in agreement with experimental data, suggesting that the changes in enzyme activity were caused by corresponding changes in the rate of synthesis. A protein of unknown function (Protein X), which is tightly associated with UDP-apiose synthase and co-purifies with the enzyme at a molar ratio of 1:1, is shown to be regulated independently of the enzymes of the flavonoid glycoside pathway.

Carboxy-Lyases↗
PubMed1979

Enzymes of General Phenylpropanoid Metabolism and of Flavonoid Glycoside Biosynthesis in Parsley: Differential Inducibility by Light during the Growth of Cell Suspension Cultures.

Several enzymes of phenylpropanoid metabolism showed large changes in their inducibility by light during the growth cycle of cell suspension cultures from parsley (Petroselinum hortense Hoffm.). Two of the three enzymes of general phenylpropanoid metabolism (group I) and six of the approximately 13 enzymes of the flavone and flavonol glycoside pathways (group II) were investigated. Both enzymes of group I (phenylalanine ammonia-lyase and 4-coumarate:coenzyme A ligase) were most efficiently induced at two different stages: first, soon after starting a new culture, and second, near the beginning of the stationary phase. In contrast, the enzymes of group II (acetyl-coenzyme A carboxylase, flavanone synthase, chalcone isomerase, UDP-apiose synthase, and at least one of two malonyltransferases) were maximally induced during exponential growth of the culture. This result supports the conclusions drawn from previous data that the two groups are regulated differentially and that the enzymes within each group are regulated in a coordinated manner.

Journal Article↗
PubMed1978

Reaction to phytotoxins in a potato population derived from mesophyll protoplasts.

Alternaria solani, the causal agent of early blight disease in potato, produces two host-specific, lipidlike toxins in culture. Both compounds are required in the leaf bioassay for the elicitation of typical early blight symptoms, but the compounds are individually inactive. The procedures for the preparation of both compounds are outlined. These compounds can be used effectively to select for toxin-insensitive and sensitive clones of a Russet Burbank potato cultivar that have been regenerated from single mesophyll protoplasts. Furthermore, both sensitivity and insensitivity to the toxins in these clones is well correlated with susceptibility and resistance to A. solani. Potato clones that have been produced by somatic cell regeneration techniques maintain their reaction type to these fungal toxins for at least two generations of vegetative propagation. The genetic basis for this variation among these potato clones remains to be explained.

Journal Article↗
PubMed1978

Serinol phosphate as an intermediate in serinol formation in sugarcane.

A novel compound, serinol phosphate, was identified in sugarcane (Saccharum officinarum) clone 51NG97. It was produced by an enzyme-mediated transamination of dihydroxyacetone phosphate with either alanine, glutamate, aspartate, or glutamine serving equally well as an amino donor. Some detectable phosphatase activity was present in crude leaf enzyme preparation that hydrolyzed serinol phosphate. A proposal for a pathway of the biosynthesis of serinol in sugarcane was formulated.Serinol can serve as an "activator" of toxin production in attenuated cultures of the sugarcane pathogen Helminthosporium sacchari and it is present in susceptible clone 51NG97. Resistant clone H50-7209 does not possess serinol and likewise no dihydroxyacetone phosphate transaminase activity could be demonstrated in enzyme preparations of this clone. The concept of toxin activation in attenuated fungus cultures is briefly discussed relative to disease resistance and susceptibility.

Journal Article↗
PubMed1977

UDP-apiose/UDP-xylose synthase. Subunit composition and binding studies.

The UDP-apiose/UDP-xylose synthase from cell suspension cultures of parsley has been purified 1400-fold by an improved method. The ratio of apiose to xylose formed from UDP-D-glucuronic acid (UDP-GlcUA) remained constant throughout the purification procedure. Dodecylsulfate-gel electrophoresis and sedimentation equilibrium measurements showed that this enzyme preparation is composed of two proteins with molecular weights of 65000 and 86000. The two proteins which are present in a molar ratio of about 1:0.7 to 1:0.9 could not be separated by ammonium sulfate fractionation, chromatography on DEAE-cellulose at different pH-values, and on omega-aminoalkyl-Sepharose, and by gel filtration on Acrylex P-100. Each protein is composed of two apparently identical subunits. The presence of only two different subunits was confirmed by end group analysis in which glycine was found as N-terminal amino acid for the larger and lysine for the smaller protein. Crosslinking with dimethylsuberimidate gave dimers of the identical subunits but no hybrids. Separation of the two proteins was achieved on DEAE-cellulose in the presence of urea. After dialysis only the 86000-Mr protein showed enzyme activity with no significant change in the apiose/xylose ratio. However, in the absence of the 65000-Mr protein enzyme stability was decreased drastically. By equilibrium dialysis it was found that 0.5 mol UDP-GlcUA are bound per mole of 86000-Mr protein. NAD+ alone was not bound, but in the presence of UDP it was also bound in a ratio of 0.5 mol/mol catalytic protein. Experiments in which sodium borohydride was added to the enzyme incubation gave no indication that the 4-keto intermediate is bound as a Schiff base to the enzyme. Also no evidence for epimerization at C-3 of the 4-ulose intermediate prior to ring contraction to apiose was found.

Carboxy-Lyases↗
PubMedDate not supplied

Ergonomics: requirements for adjusting the height of laparoscopic operating tables.

BACKGROUND AND OBJECTIVES: In the last few years many new instruments and devices have been developed and introduced into the operating room (OR). A debate has been ongoing about the optimal ergonomic posture for the operating staff. From practical experience, we have learned that the operating tables cannot be adjusted adequately to allow surgeons of different stature to maintain a comfortable posture. The goal of this study was to establish the most ergonomic table height for the particular physique of the surgeon and the different types of laparoscopic instrument handles that he or she uses. METHODS: In a simulated model, two probands of different stature (50th [BS 50] and 95th [BS 95] percentile) used laparoscopic instruments with four different handle designs (shank, pistol, axial, and rod). The instruments were inserted into a board in three different angles ([IA] = 20 degrees, 30 degrees, 40 degrees). Additionally the elbow angles (EA) of the volunteers were fixed to either 90 degrees or 120 degrees. For every variable (size of surgeon and his or her elbow angle, design of handle, insertion angle of the instrument) the height of the board, as a parameter for the level of the abdominal wall of a patient with pneumoperitioneum, was measured from the floor. RESULTS: All parameters had an effect on the optimal operating table height. The lowest required operating table level was 30 cm, the highest was 60.5 cm. In laparoscopic surgery-long shafted instruments and patients with pneumoperitoneum-the tabletops are too high for over 95% of all surgeons. As skin incision and wound suture are performed the conventional way, the operating tabletop must be adjustable up to the common height of 122 cm. The maximal difference between the optimal heights of the OR-table for one volunteer using two different handles with different insertion angles of the instruments (BS 95, EA 90 degrees, IA 20 degrees, rod handle to BS 50, EA 120 degrees, IA 40 degrees, axial handle) was about 27 cm. CONCLUSION: New operating tables with a much lower adjustability are necessary to fulfill ergonomic requirements. The use of differently designed handles can hinder the ergonomic posture of the surgeon, because each handle requires a different working height.

Equipment Design↗