Abstract
Activities of the glycolytic enzymes were determined in seedlings, callus cultures and cell sus pension cultures of spruce (Picea abies) (L.) (Karst). The rate-limiting enzymes of the pathway were the hexokinases, ATP: phosphofructo-kinase, fructose-1,6-bisphosphatase and pyruvate kinase. Two phosphofructokinases were found: ATP : fructose-6-phosphate 1-phosphotransferase (PFK) and pyrophosphate :fructose-6-phosphate 1-phosphotransferase (PFP). In the presence of its activator fructose-2,6-bisphos-phate, PFP had a 4 -5-fold higher specific activity than PFK. PFP could be activated about 20-fold by fructose-2,6-bisphosphate at saturating concentrations of the substrates (fructose-6-phosphate and pyrophosphate). The increase of Vmax was accompanied by a strong increase in the apparent affinity of the enzyme for the substrates. Km for fructose-6-phosphate and pyrophosphate was 0.44 mM and 24 μM, respectively. Ka for fructose-2,6-bisphosphate was 24 nM.
In seedlings, specific activity of the glycolytic enzymes was 30-300 percent higher in the hypocotyls, except for fructose-1,6-bisphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase, their activity being 100-150percent higher in the cotyledons, This distribution remained unchanged during periods of 2 -16 weeks of cultivation of the seedlings.
In callus cultures and in cell suspension cultures, grown mixotrophically with different car bohydrates, all enzymes were between 1-and 7-fold higher than in autotrophically grown seed lings. Incubation of seedlings in mineral salt mixture containing a carbohydrate resulted in a rapid coordinate increase of the activities to the levels of callus-or cell suspension cultures. This induction required a carbohydrate and oxygen. During prolonged cultivation of cell suspension cultures, when carbohydrate became limiting, activity of the enzymes slowly declined.
Induction of Somatic Embryos and Plantlet Development in Cell Suspension Cultures of Arachis hypogaea L.