Abstract:
Using the radiometric method, the activity of acetylcholinesterase (AChE, E.C. 3.1.1.7) was studied in seedlings of wild type (WT) and of
phytochrome mutants of tomato (Lycopersicon esculentum Mill.). The activity of this enzyme was inhibited by an excess of substrate and by
two well-known inhibitors of animal AChE, eserine and neostigmine. The activity of AChE was found in all etiolated organs as well as in
light-grown seedlings. Under both conditions, the highest level of the enzyme activity was detected in cotyledons and the lowest one in root
tissue. The enzyme activity was phytochrome-controlled. In WT etiolated seedlings red (R) light decreased AChE activity, whereas far red
(FR) light abolished the red light effect. Furthermore, in light-grownWTseedlings the level of the enzyme activity was about twice higher than
in etiolated plants. However, in the aurea phytochrome mutant of tomato, deficient in biosynthesis of a phytochrome chromophore, light had
no effect on theAChE activity. In case of hp, fri and tri mutant seedlings, R and FR affected theAChE activity in a different way. Based on our
results, we suggest that the type I of phytochrome is involved in the regulation of AChE activity. The type II of this photoreceptor influences
the rate of the AChE synthesis de novo.