Effect of calcium, manganese and lithium on growth and cardenolide content in cell suspension cultures of Digitalis thapsi L.

Cell suspension cultures of Digitalis thapsi were grown in Murashige and Skoog medium under continuous light. The effects of the absence of CaCl2, elevation of the MnSO4 concentration from 0.1 mM to 5 mM or the addition of 100 µM LiCl on their growth and digoxin production were investigated. The elimination of calcium reduced growth and viability of cultures but promoted digoxin formation. An increase of the MnSO4 concentration or the addition of LiCl resulted in higher digoxin content. Under such conditions growth was not affected.

Purification and characterization of an alpha-amylase from the cotyledons of germinating lentils.

alpha-Amylase from the cotyledons of lentils germinated for 6 days (Lens culinaris, Medik) was purified by heat treatment, complexing with glycogen, Sephadex G-75 filtration and electrofocusing. Although three bands with alpha-amylase activity were separated in the purified extract from Sephadex G-75 filtration by polyacrylamide gel electrophoresis, only one alpha-amylase fraction was obtained by electrofocusing, which appeared free of contaminating proteins in the electrophoretic pattern. The purified enzyme had maximum activity at pH 5.4, an activation energy of 5.8 kcal/mol, a km for soluble starch of 3.4 X 10(-4) g/ml, an isoelectric point of 4.8 and a molecular weight of 43,000. The pH and temperature stability of the enzyme and the effect of calcium and mercuric ions on the enzyme activity and stability were also studied.

Starch degradation during germination of Civer arietinum L. seeds.

The variations in starch and soluble sugar content, in phosphorylase and amylase activities in cotyledons of germinating seeds of Cicer arietinum L. are determined. Results from various experiments prove that the alpha-amylases are chiefly responsible for amylase activity. Phosphorylase plays an important rôle during the first two days of germination, but it is relegated to a secondary position as the amylase activity increases. Disc electrophoresis on polyacrylamide gel shows the existence of a phosphorylase throughout germination, and detects two alpha-amylases after 48 and 96 h germination respectively. The increase in alpha-amylase activity during germination is due to de novo synthesis of the two isoenzymes, since both are inhibited by cycloheximide and actinomyces D. This de novo synthesis depends on some embryo produced factor, unreplaceable either by giberellic acid or by kinetin.