M.J.C. Rhodes

Deglycosylation of flavonoid and isoflavonoid glycosides by human small intestine and liver β-glucosidase activity

Flavonoid and isoflavonoid glycosides are common dietary phenolics which may be absorbed from the small intestine of humans. The ability of cell‐free extracts from human small intestine and liver to deglycosylate various (iso)flavonoid glycosides was investigated. Quercetin 4′‐glucoside, naringenin 7‐glucoside, apigenin 7‐glucoside, genistein 7‐glucoside and daidzein 7‐glucoside were rapidly deglycosylated by both tissue extracts, whereas quercetin 3,4′‐diglucoside, quercetin 3‐glucoside, kaempferol 3‐glucoside, quercetin 3‐rhamnoglucoside and naringenin 7‐rhamnoglucoside remained unchanged. The K m for hydrolysis of quercetin 4′‐glucoside and genistein 7‐glucoside was ∼32±12 and ∼14±3 μM in both tissues respectively. The enzymatic activity of the cell‐free extracts exhibits similar properties to the cytosolic broad‐specificity β‐glucosidase previously described in mammals.

Alkaloid production by transformed root cultures of Catharanthus roseus

Transformed roots of Catharanthus roseus were obtained following infection of detached leaves with Agrobacterium rhizogenes. Roots would not grow in full strength Gamborgs B5 medium but would grow satisfactorily if the medium was diluted to one half strength. Little alkaloid appeared in the growth medium but root tissue contained a high level and wide variety of alkaloids. Ajmalicine, serpentine, vindolinine and catharanthine were prominent components. Vinblastine could also be detected by a combination of HPLC and radioimmunoassay, though at a level of only 0.05μg/g dry weight.

Stimulation of phenolic acid and lignin biosynthesis in swede root tissue by ethylene

Abstract Experiments using 14 C-phenylalanine have shown that ethylene treatment of swede root tissue promotes the utilization of phenylalanine as a precurso

The production of anthraquinones by cell suspension cultures of Cinchona ledgeriana

In a suspension culture of Cinchona ledgeriana a range of anthraquinones accumulate. Fifteen aglycone components of this fraction have been identified, six of which (anthragallol-1,2,3-trimethyl ether, 1,4,5-trihydroxy-2 methylanthraquinone, 5-hydroxy-2-methylanthraquinone, 1,5-dimethoxy-2,3-methylenedioxyanthraquinone, 2,4,6-trihydroxy-1,3-dimethoxyanthraquinone and 1,2,5,6-tetramethoxyanthraquinone) have not previously been found in this species. The time course of anthraquinone production follows neither the growth of the cells nor alkaloid synthesis The anthraquinones are exported from the cells, with about 80 % of the aglycones present normally being recovered from the medium. High levels in the medium are found to inhibit growth of the culture. The final level accumulated shown to be dependent on a number of nutritional factors, the best yield being obtained when cells are grown with the growth regulators IBA (0.5 mg/l) and ZR (0.1 mg/l) present. Effectors ofthe shikimic acid pathway such as tryptophan and glyphosate are found to inhibit anthraquinone accumulation.

Multiple forms of hydroxycinnamate : CoA ligase in etiolated pea seedlings

Abstract A survey of a range of plant tissues showed that the hydroxycinnamate CoA ligase in crude extracts of pea shoots had a high relative activity towards sinapic and other methoxycinnamic acids, together with high activity with p-coumaric acid. The pea enzyme has been resolved by chromatography on DEAE-cellulose into two peaks which differ in their substrate specificity. The form which elutes at relatively low salt concentrations has a ratio activity towards p-coumaric and sinapic acids of about 1.8:1 while the form eluting at higher salt concentrations, although showing very high activity with p-coumaric acid, is inactive towards sinapic acid. The pattern of elution of these forms following gel filtration on Ultragel AcA 34 and Sephadex G100 suggests that these two isoenzymes which differ in ionic properties and substrate specificity can exist in two or three molecular weight forms and there is evidence that these forms are under certain circumstances interconvertible.

Metabolic changes in excised fruit tissue—III. The development of ethylene biosynthesis during the ageing of disks of apple peel

Abstract The production of ethylene by disks of peel from pre-climacteric apples is induced by ageing the disks aerobically at 25°. The development of the ethylene-producing system is dependent upon protein synthesis. Ethylene evolution is stimulated by peroxidation products from linolenic acid, but not by methionine. The relationship between changes occurring during the ageing of pre-climacteric apple peel disks during the development of the climacteric in whole fruit is discussed. A rapid and sensitive method for the determination of ethylene is described.

Purification and properties of hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase from potatoes

Abstract A rapid method for the purification of hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase (CQT) from potato tubers which had been stored at low temperatures is described. The method involves affinity chromatography on Blue Sepharose with biospecific desorption of CQT with its substrate, CoA. Elution of the Blue Sepharose column with a gradient of CoA leads to the resolution of CQT, a protein with MW of ca 41500, into 3 peaks of activity; the largest peak elutes first. This fraction is purified × 1440 and gives a single band of protein after PAGE which suggests a high degree of purity. The properties of the 3 fractions of CQT, with respect to substrates and to a number of inhibitors, are described. The first and last eluting CQT fractions are specific for quinate and show no activity towards shikimate. The second peak, however, shows a small activity towards shikimate but this is thought to be due to an underlying peak of a shikimate specific enzyme. The major peak of CQT activity found in potatoes stored at 0° is absent from those stored at 10° throughout the period after harvest.

The relationship between ethylene and the synthesis of RNA and protein in ripening apples

Abstract The stimulation by ethylene of the respiration of whole fruits and peel discs prepared from them is followed using Worcester Pearmain and Coxs Orange Pippin apples. RNA and protein synthesis in relation to ethylene stimulation is investigated in terms of incorporation of 14 C-uridine and 14 C-valine into RNA and protein fractions in the discs of peel. Application of ethylene (40–60 ppm) to the preclimacteric fruit induces increased ethylene production in the fruit; uridine incorporation into RNA rises to a peak followed by a peak in valine incorporation into protein, while a malate decarboxylating system develops in the ripening fruit.

α-Acid degradation by suspension culture cells of humulus lupulus

Abstract In a suspension culture of Humulus lupulus hop α-acids could not be detected. However, the culture was shown to have an in vivo ability to degrade exogenous α-acids and related compounds. It is shown that this is due to peroxidase with a rate constant for α-acid degradation of 2.7 × 104/M · sec.

Purification and properties of phosphofructokinase from fruits of Lycopersicon esculentum

Abstract A procedure is described using affinity chromatography on Blue Sepharose and on an immobilized ATP column by which phosphofructokinase has been purified by 260-fold from tomato fruits. The properties of the enzyme are affected by the pH at which the preparation is made and maintained. At the pH optimum, pH 8.0, the enzyme is very heterogeneous with up to three forms present differing in MW. At pH 7.5 a single major form of MW 180 000 is present, and evidence that raising the pH to 8.0 promotes dissociation of the enzyme is discussed.