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PubMed1968

Properties of ribulose-1,5-diphosphate carboxylase (carboxydismutase) from Chinese cabbage and photosynthetic microorganisms.

Ribulose-1,5-diphosphate carboxylase (carboxydismutase) was prepared from Chinese Cabbage [Brassica petsai (Parl)] and the K(m) values and molecular weight were determined. These parameters were found to be in good agreement with values reported for this enzyme from other higher plants. Investigation of carboxydismutase activity from the photosynthetic micro-organisms Chlamydomonas reinhardi (IU 89+), Plectonema boryanum (IU 594), and Chromatium strain D showed striking similarity to the higher plant enzyme, when the sedimentation coefficients were compared.

Carboxy-Lyases↗
PubMed1969

The respiratory chain of plant mitochondria. I. Electron transport between succinate and oxygen in skunk cabbage mitochondria.

The kinetics of oxidation of ubiquinone, flavoprotein, cytochrome c, and the cytochrome b complex in skunk cabbage (Symplocarpus foetidus) mitochondria made anaerobic with succinate have been measured spectrophotometrically and fluorimetrically in the absence of respiratory inhibitor and in the presence of cyanide or antimycin A. No component identifiable by these means was oxidized rapidly enough in the presence of one or the other inhibitor to qualify for the role of alternate oxidase. Cycles of oxidation and rereduction of flavoprotein and ubiquinone obtained by injecting 12 mum oxygen into the anaerobic mitochondrial suspension were kinetically indistinguishable in the presence of cyanide or antimycin A, implying that these 2 components are part of a respiratory pathway between succinate and oxygen which does not involve the cytochromes and does involve a cyanide-insensitive alternate oxidase. The cytochrome b complex shows biphasic oxidation kinetics with half times of 0.018 sec and 0.4 sec in the absence of inhibitor, which increase to 0.2 sec and 1 sec in the presence of cyanide. In the presence of antimycin A, the oxidation of the cytochrome b complex shows an induction period of 1 sec and a half-time of 3.5 sec. A split respiratory chain with 2 terminal oxidases and a branch point between the cytochromes and flavoprotein and ubiquinone is proposed for these mitochondria.

Electron Transport↗
PubMed1969

Effects of freezing and hardening on the sulfhydryl groups of protein fractions from cabbage leaves.

Disc electrophoresis was used to separate water soluble proteins from hardy, non-hardy, and frost killed cabbage (Brassica oleracea var. capitata) leaves. Amidoschwarz staining failed to reveal any new bands as a result of hardening although the relative amounts of proteins in individual bands changed. Sulfhydryl groups in the protein bands were stained with 2,2-dihydroxy-6,6-dinaphthyl disulfide and labeled with (14)C p-chloromercuribenzoate. Significant decreases in the sulfhydryl content of the total water soluble protein were found during hardening and as a result of frost death. The decrease during hardening was paralleled by a significant increase in the water soluble protein. There was a significant increase in the sulfhydryl content per unit high molecular weight protein but a decrease in the sulfhydryl content per total protein as a result of frost death. This was interpreted as evidence for intermolecular disulfide bond formation during freezing.

Journal Article↗
PubMed1969

Translocation of sugars into infected cabbage tissues during clubroot development.

Sucrose, glucose, and inositol were the major sugars in cabbage hypocotyls infected by Plasmodiophora brassicae and in noninfected hypocotyls, based on paper, thin-layer, and gas-liquid chromatography. Small amounts of trehalose were tentatively identified in extracts from noninfected hypocotyls, whereas up to 20x this level occurred in extracts from infected hypocotyls. Inositol declined in the infected hypocotyls while glucose increased to about 4x the level in noninfected hypocotyls. Fructose and mannose concentrations increased about 2-fold in the diseased hypocotyls, whereas the galactose concentration was about one-third that of noninfected hypocotyls.Translocation of (14)CO(2) sugar photosynthates into infected hypocotyls was more rapid than that into noninfected hypocotyls. The infected tissues also exported less sugar than the non-infected tissues. Sucrose was the major sugar translocated into the hypocotyls of both infected and noninfected plants.

Journal Article↗
PubMed1969

Direct relation between growth and frost hardening in cabbage leaves.

Potted cabbage plants were grown in growth chambers at 25 degrees day and 15 degrees night and hardened successively at 5, 0, and -3 degrees . Leaf growth was determined by measuring leaf area, hardiness by freezing at a series of temperatures and determining percent survival. Leaf growth increased progessively with leaf number, reaching a maximum rate of growth and final area in the tenth and eleventh leaves when the plants become potbound. Leaf growth continued at hardening temperatures of 5 or 0 degrees , the Q(10) being 2.0 to 2.5. Ability to harden also increased with leaf number, paralleling the growth rate of the leaves just before hardening as well as the growth rate and the total growth during hardening. The above results were similar whether prolonged (several weeks) or brief (24 hr) hardening was utilized.

Journal Article↗
PubMed1970

The Respiratory Chain of Plant Mitochondria: VII. Kinetics of Flavoprotein Oxidation in Skunk Cabbage Mitochondria.

The oxidation kinetics of the two high potential flavo-proteins, one (Fp(hf)) fluorescent and the other (Fp(ha)) nonfluorescent, in mitochondria from skunk cabbage (Symplocarpus foetidus) spadices have been measured by combined spectrophotometry and fluorimetry. In the absence of respiratory inhibitors, both flavoproteins are oxidized at nearly the same rate with half-times between 120 and 160 milliseconds at 24 C. When slight differences in rate are observed, it is Fp(ha) which consistently has the shorter half-time. The presence of 0.3 millimolar KCN has no perceptible effect on the oxidation rate of either component. Antimycin A (2 nanomoles per milligram of protein) increases the oxidation half-time of Fp(ha) about 3-fold, but it has no effect on the oxidation half-time of Fp(hf). In contrast to these two inhibitors, m-chlorobenzhydroxamic acid-an inhibitor specific to the cyanide insensitive, alternate oxidase pathway in these mitochondria-increases the oxidation half-time of Fp(hf) 10-fold to about 2 seconds, while increasing that of Fp(ha) only some 20%. This result implies that the flavoprotein Fp(hf) mediates electron transport to the alternate oxidase from the region of the mitochondrial respiratory chain encompassing Fp(ha), ubiquinone, and the cytochromes b. The oxidation rate of cytochrome b(557) is unaffected by either m-chlorobenzhydroxamic acid or cyanide but is strongly inhibited by antimycin A. This result implies that cytochrome b(557) plays no direct role in the respiratory pathway to the alternate oxidase and is different from cytochrome b(7) found in mitochondria from the spadices of Arum maculatum.

Journal Article↗
PubMed1971

Kinetin and carbohydrate metabolism in chinese cabbage.

The effects of kinetin on starch and sugar levels and on (14)CO(2) and (32)P-orthophosphate labeling patterns of floated Chinese cabbage (Brassica pekinensis) leaf discs were investigated. Kinetin caused gross starch degradation. Neutral sugars were depressed by 30 to 40% in leaf tissue treated with kinetin for 24 hours. (14)CO(2) labeling of leaf discs pretreated with kinetin for 24 hours showed increased radioactivity in chloroform-soluble material and most sugar phosphates, and a 35 to 40% decrease in radioactivity in the neutral sugars, glucose, sucrose, and fructose. Incorporation into ATP was increased by 40% by kinetin. (32)P-Orthophosphate uptake was inhibited 30% by kinetin. When corrected for uptake, kinetin stimulated incorporation into chloroform-soluble material but had little effect on other cell fractions. These results indicate that kinetin mobilizes starch reserves and increases the flow of sugars required for the synthesis of lipids and structural materials in floated discs.

Journal Article↗
PubMed1971

The respiratory chain of plant mitochondria: x. Oxidation-reduction potentials of the flavoproteins of skunk cabbage mitochondria.

The oxidation-reduction potentials of the flavoproteins of skunk cabbage (Symplocarpus foetidus) mitochondria have been measured under anaerobic conditions by means of a combined spectrophotometric or fluorimetric-potentiometric method. Five components were resolved whose oxidation-reduction reactions corresponded to two-electron changes, as expected for flavoproteins. The midpoint potentials at pH 7.2 are as follows, listed in order of increasingly negative potential: +170 millivolts, +110 millivolts, +20 millivolts, -70 millivolts, and -155 millivolts. The most negative component was highly fluorescent; the other components could only be identified by their characteristic absorbance changes. In addition to these components, which are mitochondrial, variable amounts of a very highly fluorescent flavoprotein with a midpoint potential of -215 millivolts was found. This component appears to be extra-mitochondrial. The same midpoint potential values at pH 7.2 were obtained with mitochondria in the uncoupled state as in mitochondria energized with ATP in the absence of phosphate.

Journal Article↗
PubMed1974

The Respiratory Chain of Plant Mitochondria: XVII. Flavoprotein-Cytochrome b(562) Interaction in Antimycin-treated Skunk Cabbage Mitochondria.

During the transition from the aerobic steady state with succinate as substrate to anaerobiosis, in suspensions of skunk cabbage (Symplocarpus foetidus) mitochondria treated with antimycin A, cytochrome b(562) becomes reoxidized to the extent of about 20%, synchronously with the reduction of cytochrome c(549). This reoxidation occurs in both the absence and presence of m-chlorobenzhydroxamic acid, a specific inhibitor for the alternate terminal oxidase of plant mitochondria. A flavoprotein component, amounting to 13% to 15% of the total nonfluorescent mitochondrial flavoprotein, undergoes reduction synchronously with the oxidation of cytochrome b(562) during the aerobic to anaerobic transition with succinate as substrate in the presence of both antimycin A and m-chlorobenzhydroxamic acid. This flavoprotein component remains reduced in the presence of cyanide. The half-time for reduction of the flavoprotein component and cytochrome c(549) and for oxidation of cytochrome b(562) during the aerobic to anaerobic transition with succinate as substrate in the presence of both antimycin A and m-chlorobenzhydroxamic acid is 2 seconds. The half-times for oxidation of cytochrome c(549) and the flavoprotein component are 2.1 and 170 milliseconds, respectively, during the anaerobic to aerobic transition induced by addition of 14 mum O(2) to the mitochondrial suspensions. The half-time for reduction of cytochrome b(562) under these conditions is 150 milliseconds, synchronous with the flavoprotein component. The synchrony of the flavoprotein oxidation and of the cytochrome b(562) reduction at a rate much slower than that of cytochrome c(549) oxidation implies that, in antimycin-treated plant mitochondria, the state of the cytochrome b(562)/antimycin complex is regulated by the redox state of this flavoprotein component, rather than by cytochrome c(549). It is tentatively suggested that these two components are not part of the main sequence of the respiratory chain, but may be part of a multienzyme complex active in the hydroxylation reactions required for ubiquinone biosynthesis in the inner mitochondrial membrane.

Journal Article↗
PubMed1976

Interrelations between Environmental Factors and Freezing Resistance of Cabbage Leaves.

Rapid wilting of cabbage leaves (Brassica capitata L.), induced by excision of the shoot, induced as rapid and high a degree of freezing resistance as a similar period of hardening at low temperature. Maximum hardening in the leaf was generally associated with the maximum growth rate. On the other hand, exposure of the excised shoot to low temperature while immersed in aerated water failed to harden the plants. In the absence of light, abrupt wilting at room or low temperature induced little or no hardening. With the available equipment, which required the absence of light, freezing temperatures induced little or no hardening above that obtained by nonfreezing low temperature. In fact, the plant frozen at moderate temperatures showed a gradual but steady decrease in freezing resistance. Since these experiments were performed with plants grown in pots, and since they eventually became pot-bound, the results may not apply equally to field-grown plants.

Journal Article↗
PubMed1977

Evidence that root pressure flow is required for calcium transport to head leaves of cabbage.

Young cabbage plants (Brassica oleracea L. var. capitata) that were exposed to an atmosphere at 50% relative humidity transpired freely and accumulated significant quantities of (45)Ca in the leaves. Plants that were enclosed by plastic bags to stop transpiration from all leaves exhibited guttation with the development of root pressure and also accumulated significant quantities of (45)Ca in the leaves. (45)Ca accumulation increased in the leaves and tended to decrease in roots and stems with increasing quantities of water transpired or guttated by the plant. When plants were only partially enclosed so that some leaves were covered and the remainder exposed, only the exposed leaves that were transpiring accumulated significant quantities of (45)Ca. The covered leaves of partially enclosed plants exhibited no guttation and accumulated little (45)Ca with no measurable (45)Ca at the margins of the leaves. The results demonstrate that root pressure flow is required to transport adequate amounts of Ca to those tissues in plants that are not undergoing transpirational water loss.

Journal Article↗
PubMed1981

The synthesis of polyamines from methionine in intact and disrupted leaf protoplasts of virus-infected chinese cabbage.

In exploring the role of the chloroplast in the multiplication of turnip yellow mosaic virus, the biosyntheses of the major viral polyamine, spermidine, as well as that of the tetramine, spermine were studied. The synthesis of these polyamines from [2-(14)C]methionine in protoplasts of Chinese cabbage leaf cells derived from healthy plants or those infected by turnip yellow mosaic virus were examined. Populations of protoplasts of infected leaves are homogeneous with respect to containing chloroplast aggregates in contrast to those of healthy leaves. Protoplast preparations have been shown to incorporate methionine into protein, spermidine, and spermine more rapidly than do fresh leaf discs, which also show a very slow utilization of labeled arginine and ornithine into polyamine.Protein synthesis is similar for 4 hours in both healthy and infected protoplasts. Accumulation of labeled spermidine stops after 2 hours in healthy protoplasts but continues in the infected protoplasts. Much of the newly synthesized protein and spermidine is present in the easily sedimentable fraction of the readily disrupted protoplasts.Disrupted and diluted protoplasts have a decreased ability to metabolize methionine to protein and spermidine. The residual synthetic activity is essentially entirely in the easily sedimentable fraction. However, this fraction is unable to synthesize spermine, an activity found in protoplasts and disrupted protoplasts. Disrupted protoplasts contain spermidine synthase (EC 2.5.1.16) and about a quarter of this activity is present in a low-speed sedimentable fraction containing the chloroplasts. The protoplast system is suitable for an analysis of polyamine synthesis in turnip yellow mosaic virus infection and appears particularly suitable for study of the distribution of the enzymes involved.

Journal Article↗
PubMed1982

ATP sulfurylase from higher plants : purification and preliminary kinetics studies on the cabbage leaf enzyme.

ATP sulfurylase was purified extensively from green cabbage (Brassica capitata L.) leaf. The enzyme appears to be an asymmetric dimer composed of 57,000 dalton subunits. Initial velocity and product inhibition studies of the forward and reverse reactions point to an obligately ordered kinetic mechanism with MgATP adding before MoO(4) (2-) (or SO(4) (2-)). and MgPPi leaving before AMP + MoO(4) (2-) (or adenosine-5'-phosphosulfate [APS]). The addition of excess purified fungal APS kinase to assay mixtures increased the rate of (35)SO(4) (2-) incorporation and MgPPi formation and extended the linearity of the forward reaction. This effect can be ascribed to the continual removal of APS, a potent product inhibitor of ATP sulfurylase. The specific activities of the enzyme in the APS synthesis, molybdolysis, MgATP synthesis, and sulfate-dependent [(32)P]-MgPPi-MgATP exchange assays were 3.3, 38, 38, and 4.3 micromole product formed per minute per milligram protein, respectively.

Journal Article↗
PubMed1983

Partial Purification and Characterization of Cystine Lyase from Cabbage (Brassica oleracea var capitata).

Cabbage (Brassica oleracea var capitata) leaves were used as a source of cystine lyase. Diethylaminoethyl-cellulose chromatography resolved two peaks of activity, designated I and II.Cystine lyase I (molecular weight 145,000) and O-acetylserine sulfhydrylase (molecular weight 70,000) were resolved by Bio-Gel A-0.5M chromatography. This isozyme catalyzed an alpha,beta-elimination reaction with cystine, cysteine, O-acetylserine, and several S-substituted cysteines. The substrate specificity was similar to previously reported S-alkylcysteine lyases. The elution profiles during purification, and heat inactivation studies indicated that the above reactions were catalyzed by a single protein. The pH optimun with cystine and cysteine as substrate was 8.5 to 9.0, and the K(m) values were: cystine (0.3 mm), cysteine (0.3 mm), O-acetylserine (6 mm), and S-methylcysteine sulfoxide (1.8 mm).Cystine lyase II was resolved into three peaks (molecular weight greater than 500,000, 240,000, and 145,000) using Bio-Gel A-0.5M chromatography. This enzyme degraded l-cystine, l-cysteine, O-acetylserine, S-methylcysteine sulfoxide, and djenkolic acid. The pH optimum with cystine and cysteine was 8.5 to 9.0, and the K(m) values were: cystine (0.3 mm), cysteine (0.3 mm), O-acetylserine (12.5 mm), and S-methylcysteine sulfoxide (3.7 mm).

Journal Article↗
PubMed1984

Subcellular localization of spermidine synthase in the protoplasts of chinese cabbage leaves.

Previous studies on the presence of spermidine synthase (EC 2.5.1.16) in the protoplasts of Chinese cabbage (Brassica pekinensis var Pak Choy) leaves had detected a small but significant fraction of the enzyme in a crude chloroplast fraction (Cohen, Balint, Sindhu 1981 Plant Physiol 68: 1150-1155). To establish whether this enzyme is truly a chloroplast component, we have isolated purified intact chloroplasts from protoplasts by density gradient centrifugation in silica sols (Ludox AM). Such chloroplasts contained all of the diaminopimelate decarboxylase (EC 4.1.1.20) of the protoplasts, but were essentially devoid of spermidine synthase. Control experiments showed that the latter had not been inactivated under conditions of isolation, purification, and assay of the intact chloroplasts. Isolation and assay of protoplast vacuoles in a further examination of the supernatant fluid containing the enzyme revealed a significant fraction of the enzyme in the vacuole fraction. However this fraction was found to contain similar proportions of a soluble enzyme, glucose 6-phosphate dehydrogenase. It has been concluded that vacuolar fractions are difficultly separable from soluble cytoplasmic material, which is probably the only compartment containing spermidine synthase.

Journal Article↗
PubMed1989

Water relations of turgor recovery and restiffening of wilted cabbage leaves in the absence of water uptake.

A novel phenomenon in which wilted cabbage leaves appeared to regain positive turgor pressures without additional water uptake has been previously reported (J Levitt [1986] Plant Physiol 82: 147-153). These experiments were replicated and the biophysical nature of turgor recovery characterized. Leaf water potential and its components were assayed in hydrated, wilted, and desiccated leaves which appeared to regain turgor after wilting. The hypotheses that turgor recovery was due to an increased volumetric elastic modulus (epsilon), or alternatively the result of solute redistribution were tested. Quantitative evidence that turgor recovery occurs in excised leaves was found. Leaf turgor pressure in hydrated leaves ( approximately 0.6 megapascal) decreased to zero upon wilting. After continued desiccation, turgor pressure returned to approximately 0.3 megapascal even though leaf relative water content declined. The epsilon of hydrated leaves was large and there was no evidence of an increased epsilon in the turgor-recovered leaves. Solute mobilization occurred during desiccation. The apoplastic osmotic potential decreased from -0.15 to -0.44 megapascal in hydrated and turgor-recovered leaves, respectively, and solutes were transported from the lamina to the midrib tissue. Solute redistribution coupled with the high epsilon may have resulted in localized turgor recovery in specific cells in the desiccated leaves.

Journal Article↗
PubMed1991

Isolation and Characterization of a UDPGlucose: Flavonol O-Glucosyltransferase from Illuminated Red Cabbage (Brassica oleracea cv Red Danish) Seedlings.

A UDPGlc:flavonol O(3)-glucosyltransferase (EC 2.4.1.91) that catalyzes the formation of quercetin and kaempferol O(3)-glucosides has been purified about 1450-fold from illuminated red cabbage (Brassica oleracea cv Red Danish) seedlings with a 3.3% yield. Purification of the enzyme was achieved by (NH(4))(2)SO(4)-precipitation, gel-filtration, ion-exchange chromatography on DEAE-Bio-Gel and Q-Sepharose, chromatofocusing, and electrophoresis in nondenaturing polyacrylamide (10%) gels. The enzyme preparation had a pH optimum between 5.8 and 6.2, isoelectric point in the pH range 4.25 to 4.55, a M(r) of 59,000, and it was composed of two similar subunits of M(r) 29,500. The glucosyltransferase reached half substrate saturation at 180 micromolar (UDPGlc) and 7 micromolar (quercetin) concentrations. Kaempferol, which was glucosylated at a relative rate of 87%, had a lesser affinity for the enzyme (K(m)~12 micromolar). Flavanones, flavanols, flavones, dihydroflavonols, and anthocyanidins were not readily utilized as substrates, suggesting that the enzyme is specific for flavonol glucoside biosynthesis.

Journal Article↗
PubMed1998

Purification of pierisin, an inducer of apoptosis in human gastric carcinoma cells, from cabbage butterfly, Pieris rapae.

A substance strongly cytotoxic to human carcinoma cell line TMK-1 has been found in pupae, larvae and adults of the cabbage butterfly, Pieris rapae, and named pierisin. Pierisin was purified from the pupae of P. rapae by ammonium sulfate precipitation followed by DEAE-cellulose, Phenyl-Sepharose and hydroxyapatite column chromatographies. The molecular weight of the purified pierisin, which was homogenous on SDS-polyacrylamide gel, was analyzed by mass spectrometry and found to be 98 kDa. Pierisin showed a strong cytotoxic effect, with and IC50 of 0.75 ng/ml for human gastric carcinoma TMK-1 cells. The dying cells exhibited characteristic morphological features of apoptosis, such as cell shrinkage, chromatin condensation and nuclear fragmentation. Oligonucleosomal DNA fragmentation was also observed in DNA isolated from pierisin-treated cells. Moreover, similar characteristic changes showing apoptotic cell death were observed in TMK-1 cells treated with a crude extract of pupae of P. rapae. These results indicate that pierisin from the pupae of P. rapae induces apoptosis in human carcinoma cells.

ADP Ribose Transferases↗