Peroxidases of Solanum melongena leaves

Three major peroxidases, designated as A, B₂ and B₂ from Solanum melongena leaves have been reported. Peroxidases-A, -B₂ and -B₂ were considered to be true peroxidases on the basis of k₁:k₄ ratio. The pH optima for the three enzymes were found to be 7·0, 6·0 and 6.0 respectively. These peroxidases differ in their k₁:k₄ ratio, in the effect of pH on this ratio and in the uric acid/guaiacol and o-dianisidine/guaiacol activity ratio.     

Die quantitative verteilung der sterine und sterinderivate in organen von Solanum dulcamara

The following sterols were found in the roots, stems, leaves, unripe and ripe fruits of Solanum dulcamara: cholesterol, sitosterol, stigmasterol, campesterol, brassicasterol, isofucosterol and 24-methylenecholesterol. The most abundant components are cholesterol, sitosterol and stigmasterol (77–84%). In all parts of the plant the sterols are present in the free form and as esters, glycosides and acylated glycosides. The total sterol content and the content of combined forms were determined photometrically. In the leaves 58% of the sterols were found in the form of glycoside (26%), acylated glycoside (29%) and ester (2%). In the roots only 25% of the sterol were found in combined form. In the other organs the ratio of free and combined sterols was intermediate. In all cases, the ester fraction was the least.     

Oligofurostanosides from Solanum nigrum

One spirostanol glycoside and two furostanol glycosides have been isolated from a methanol extract of the stems and roots of Solanum nigrum and ide     

Membrane-degrading enzymes in the leaves of Solanum tuberosum

When homogenates of potato leaves were prepared under conditions which are typical for organelle isolation (pH 7.5 and 4°), membrane lipids underwent rapid hydrolysis (17% of phosphatidylcholine was hydrolysed in 2 hr). Leaves of 41 potato cultivars were surveyed for phospholipase activity to determine whether certain cultivars might be more suitable for the preparation of organelles. Phospholipase activities ranged from 1.04 to 11.60, μmol/min · g fr. wt and p-nitrophenyl palmitate hydrolase activity ranged from 0.0119 to 0.0502,μmol/min · g fr. wt. These phospholipase values were several hundred-fold higher than previously reported for potato leaves and nearly as high as in potato tubers. Most of the phospholipase activity in leaves was soluble and not membrane-associated as previously reported.     

Mechanism of starch-sugar interconversion in Solanum tuberosum

The changes in glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, dihydroxyacetone phosphate, 3-phosphoglycerate, 2-phospho-glycerate, phosphoenol-pyruvate, pyruvate, adenosine mono-, di- and tri-phosphates, NAD and NADH, sugars and respiration of mature potato tubers (variety King Edward) caused by transfer from + 10° to + 2° and back to + 10° were followed throughout 4–8 weeks of storage. The results obtained showed a characteristic two phase pattern. In the case of the transfer from + 10° to + 2° a number of the phosphate esters showed wide individual variations in concentration during the first phase but only slow changes during the second phase when most of the phosphate esters tended to follow a common pattern. In the first phase the sugar concentration remained roughly constant, but in the second a considerable increase in both sucrose and respiration occurred. In the case of potatoes transferred from + 2° to + 10° the two phase character of the results was not so marked. In the case of potatoes transferred from + 10° to + 2° the changes in the phosphate esters in the first phase did not appear to be related to the conversion of starch to sucrose which only occurred to a significant extent in the second phase. Electron micrographs of potato tubers which had been stored at + 2° for 38 days (sugar content 2.4%) showed that the starch grains were still enclosed in a double membrane (amyloplast membrane). Analysis of starch grains prepared by a non-aqueous method from potato tubers stored at + 10° and + 2° indicated that a large part of the K, Na, Cl, citrate and glucose-6-phosphate was inside the amyloplast but that the sugar (storage at + 2°) was outside; sweetening therefore involved the transport of metabolites through the amyloplast membrane. Comparison with other treatments (anaerobiosis, cyanide, ethylene chlorhydrin) which cause sweetening suggested that the regulation of the starch-sugar interconversion was effected at the amyloplast membrane and possibly involved electron transfer. In the case of potatoes which sweetened due to senescence, electron micrographs showed that the amyloplast membranes were disintegrating.     

Phosphofructokinase of Solanum tuberosum tuber

Potato tuber phosphofructokinase was purified 19·.6-fold by a combination of ethanol fractionation and DEAE-cellulose column chromatography. The enzyme was very unstable; its pH optimum was 8·0. K_m for fructose-6-phosphate, ATP and Mg²⁺ was 2·1 × 10^?4 M, 4·5 × 10^?5 M and 4·0 × 10^?4 M respectively. ITP, GTP, UTP and CTP can act as phosphate donors, but are less active than ATP. Inhibition of enzyme activity by high levels of ATP was reversed by increasing the concentration of fructose-6-phosphate; the affinity of enzyme for fructose-6-phosphate decreased with increasing concentration of ATP. 5′-AMP, 3′,5′-AMP, 3′-AMP, deoxy AMP, UMP, IMP, CMP, GMP, ADP, CDP, GDP and UDP did not reverse the inhibition of enzyme by ATP. ADP, phosphoenolpyruvate and citrate inhibited phosphofructokinase activity but Pi did not affect it. Phosphofructokinase was not reactivated reversibly by mild change of pH and addition of effectors.     

Structure of solanaviol,a new steroidal alkaloid from Solanum aviculare

A new alkaloid solanaviol ((22R, 25R)-spirosol-5-ene-3β,12β-diol) was isolated from Solanum aviculare in addition to solasodine as one of the main alkaloids. The structure of solanaviol was established by NMR spectroscopy, as well as by conversion into a known pregnane derivative and solasodine.     

Starch-sugar interconversion in Solanum tuberosum

The changes in starch, sugars, and respiration of both immature and mature potato tubers (variety King Edward) caused by transfer from +10° to +2° and back to +10°, were followed throughout. At each storage temperature the tubers were allowed to reach a steady state before transfer to another temperature. In potatoes transferred from +10° to +2°, the sugar at first rose rapidly and then reached a constant value after 30 days. The respiration showed a characteristic pattern, for the first 5–8 days being below the initial value, then rising to a maximum at 14 days and finally returning to the initial value at 28 days. In potatoes transferred from +2° to +10° the sugar declined steadily, the respiration reaching a maximum after 10 days and then slowly falling to a value slightly above the initial value. Quantitative analysis of the results showed that the sum of starch + sugar + CO₂ expressed in equivalent anhydrohexose units did not change throughout the various changes in temperature. This work provided a quantitative experimental basis for what had hitherto been an assumption. Starch was the only polysaccharide involved in these carbohydrate changes. No change in the amylose/amylopectin ratio was detected either during the breakdown of starch (temperature change +10° to +2°) or during its synthesis (+2° to + 10°). The increased respiration which accompanied any change in temperature was related quantitatively to the formation of sucrose from starch (+10° to +2°) and starch from sugar (+2° to + 10°). The ATP equivalent of the extra CO₂ output was of the same order as that predicted on the basis of known biochemical pathways linking starch and sugar.     

Pigment evolution in Lycopersicon esculentum fruits during growth and ripening

During growth and subsequent maturation, the distribution and formation of pigments in the inner pulp and in the outer region of the pericarp of ‘che     

Lipoxygenase isoenzymes from Solanum tuberosum

Two lipoxygenase isoenzymes were separated from potato tubers (Solanum tuberosum). Experiments with chemical modifications showed that tryptophan is essential for enzyme activity and that one or more tryosine residues was involved. On the other hand, no lysine or sulfhydryl groups were necessary. Both enzymes had an optimum pH of 5·5. They were not affected by calcium ions but were inhibited by cysteine.     

Metabolism of cholesterol by callus culture of Holarrhena antidysenterica

A chemically defined medium was established for the growth of tissue cultures of Holarrhena antidysenterica. Administration of cholesterol-[4-¹⁴C] to 10-day-old callus yielded radioactive 24-methylenecholesterol, 28-isofucosterol, sitosterol, stigmasterol, and conessine, thereby indicating that the conversion of cholesterol into sitosterol is mediated through 24-methylenecholesterol and 28-isofucosterol in this system.     

Isolation and characterization of catechol oxidase from Solanum melongena

Catechol oxidase was distributed in soluble and particulate fractions of Solanum melongena. The purified preparation appears to be homogeneous by polyacrylamide gel electrophoresis. The enzyme shows two pH maxima—with catechol, 6.5 and 7.5; and with dopa, 6.5 and 7.9. The latent form of the enzyme does not occur in S. melongena. The preparation resembles the enzyme from other sources in substrate specificity towards various mono- and diphenols, having a higher affinity for catechol than dopa; this tendency increases on purification. The cresolase activity decreases with purification and a lag period with p-cresol is observed. The oxidation of mono- and diphenols is inhibited by ascorbic acid, sulphydryl compounds and chelating agents.     

Structural studies of two apyrases from Solanum tuberosum

The proportion of acid and basic amino acid residues obtained for two homogeneous isoenzymes of apyrase isolated from different clonal varieties of Solanum tuberosum (Pimpernel and Desirée) was essentially the same. This does not agree with the difference in pI values observed. Treatment with asparaginase and glutaminase caused partial inactivation of both enzyme activities in both isoenzymes, and pI values were changed, but not equalized. The differences in pI values of the native isoenzymes may still be attributed to different proportions of glutamine and asparagine in the primary structure. Leucine is the amino-terminal residue in both isoenzymes. Both have two disulphide bridges and one buried sulphydryl group which is not essential for enzyme activity. Differences in pI values should thus be attributed to factors other than amino acid composition.     

Properties of two apyrases from Solanum tuberosum

Two homogeneous isoenzymes of apyrase from Pimpernel and Desirée varieties of Solanum tuberosum were obtained by affinity chromatography on agarose-Cibacron Blue or agarose-ATP-phosphonate columns. Both enzymes split POP bonds of organic and inorganic di- and triphosphates. The ratio of ATPase/ADPase is different for the two apyrases: 10 for Pimpernel and 1 for Desirée. All these activities require bivalent metals. Both isoapyrases have the same MW (49 000) but differ in their pI (8.74 for Pimpernel and 6.69 for Desirée). The optimum pH of hydrolysis of organic di- and triphosphates is 6 (except for Pimpernel ADPase) and 5 for inorganic substrates. Chemical modification of tryptophan, tyrosine, arginine and carboxylic residues decreased all enzymic activities of both enzymes. Protection by substrates and inactivation rates of the individual activities are different for each isoenzyme.     

Steroidal constituents of Solanum xanthocarpum

From the extract of the fruits of Solanum xanthocarpum, cycloartanol (I), cycloartenol (II), sitosterol (III), stigmasterol (IV), campesterol (V), cholesterol (VI), sitosteryl glucoside (VII), stigmasteryl glucoside (VIII), solamargine (IX), and β-solamargine (X) were identified and an isolated steroid (XI) was identical with 4α-methyl-(24R)-ethylcholest-7-en-3β-ol synthesized from carpesterol.     

An arabinogalactoxyloglucan from the cell wall of Solanum tuberosum

Cell-wall material from potatoes was fractionated by successive extractions with water at 80°, 0.2 M (NH₄)₂C₂O₄ at 80°, 1 M and 4 M KOH, to leave a residue of α-cellulose. The compositions of the isolated carbohydrate polymers were determined by sugar and methylation analysis. From the 4M KOH-soluble fraction an arabinogalactoxyloglucan was isolated and (partially) characterized by methylation analysis of the undegraded polymer and partially degraded methylated polymer. Methylation analysis of the oligosaccharides produced on treatment of the xyloglucan with cellulase threw additional light on the structural features of the polysaccharide. The results show that the xyloglucan has a cellulosic backbone which is highly substituted at position 6 with xylopyranose residues, some of which, in turn, carry either arabinofuranose or galactopyranose residues, as a substituent on position 2. The significance of these results is discussed.     

Side chain functionalization of cholesterol in the biosynthesis of solasodine in Solanum laciniatum

(25R)-26-Amino-cholesterol-[7α-³H], (25R)-26-amino-5-cholestene-3β,16β-diol-[7α-³H] and (25R)-26-acetylamino-5-cholestene-3β,16β-diol-[7α-³H] administered to Solanum laciniatum were converted into solasodine. The results indicate that in the biosynthesis of solasodine the introduction of nitrogen occurs immediately after the hydroxylation at C-26 and before a further oxidation of the side chain of cholesterol. The next step after the amination at C-26 is not hydroxylation at the 16β-position but probably the functionalization of C-22.     

Steroidal constituents of Solanum xanthocarpum

From the extract of the fruits of Solanum xanthocarpum (Solanaceae), five new steroidal compounds were isolated and characterized: 4α-methyl-24ξ-ethyl-5α-cholest-7-en-3β,22ξ-diol (1), 3β,22ξ-dihydroxy-4α-methyl-24ξ-ethyl-5α-cholest-7-en-6-one (2), 3β-benzoxy-14β,22ξ-dihydroxy-4α-methyl-24ξ-ethyl-5α-cholest-7-en-6-one (3), 3β-benzoxy-14α,22ξ-dihydroxy-4α-methyl-24ξ-ethyl-5α-cholest-7-en-6-one (4) and 3β-(p-hydroxy)-benzoxy-22ξ-hydroxy-4α-methyl-24ξ-ethyl-5α-cholest-7-en-6-one (5).     

The effect of temperature on adenosine diphosphate glucose pyrophosphorylase from Solanum tuberosum

A partially purified extract of adenosine diphosphate glucose pyrophosphorylase has been prepared from Solanum tuberosum. The effect of temperature on the initial rate of reaction has been determined in the presence and absence of activator. The results are discussed in relation to the sweetening of potatoes at 2°.