Enzymes activity nitrogen

Bioassays are performed under sterile conditions in a laminar flow hood. Tomato seeds are previously washed and disinfected with 1% sodium hypochlorite. Seeds are germinated in the Petri dishes containing the S. deppei aqueous leachate. For control, seeds are germinated in 1% agar. Twelve seeds are placed on each Petri dish and kept in the dark at 27°C in a growth chamber. For enzyme activities, 40-50 Petri dishes are used per treatment. Primary roots (radicles) are excised after 72 h, frozen in liquid nitrogen and kept at -70 °C until use. For root growth response, experiments... 

Formally, in its oxidized state the cofactor NAD+ is charged negatively due to the two phosphate groups the positive charge denotes quaternization of the nitrogen. It is noteworthy that from the reduced form only the 1,4-NAD(P)H instead of the 1,6-NAD(P)H is enzyme-active, which imposes some restrictions on the regeneration systems in terms of the selectivity. 

B. H. Junker, J. Lonien, L. E. Heady, A. Rogers, and J. Schwender, Parallel determination of enzyme activities and in vivo fluxes in Brassica napus embryos grown on organic or inorganic nitrogen source. Phytochemistry 68, 2232 2242 (2007). 

Immobilized sialyl aldolase (50 mL of gel, 68 U) was added to a mixture of 88% pure A-acetylmannosamine (20 mmol), sodium pyruvate (180 mmol), 1,4-dithiothreitol (0.2 mmol), and sodium azide (20 mg) in 0.05 M potassium phosphate buffer, pH 7 (150 mL). The suspension was gently stirred under nitrogen for 4 d at 37°, the reaction being monitored by t.l.c. in 7 3 propanol - water. The gel was removed by filtration, washed with the buffer, and A-acetylneuraminic acid (2) was isolated by chromatography on Dowex 1 X8 (HCOj-) resin, using a gradient of formic acid as the eluant, in 66% yield. The gel was used in four successive runs. Starting from 17 g of 88% pure A-acetylmannosamine, the procedure allowed the synthesis of 14 g of A-acetylneuraminic acid (2). In the end, the recovered gel retained 80% of its enzymic activity. 

---