Cyanide Metabolism Involved in Ethylene Formation of Ripening or Wounded Fruit Tissues

Abstract

Changes in β-cyanoalanine synthase activity, rate of ethylene production, ACC and CN^-content were determined in ripening and wounded fruit tissues. When fruits were examined at various ripening stages, apple fruits which had the highest rate of ethylene production, showed the greatest activity of β-cyanoalanine synthase, while satsuma mandarin peel showed the least enzyme activity.
During maturation of apple fruit on the trees, β-cyanoalanine synthase activity gradually increased until November 29, then showed a marked increase. The CN^- content and rate of ethylene production remained at constant levels before November 29 and increased thereafter. In wounded apple tissue, the rate of ethylene produc tion reached a peak after 24 hours, while the CN^- content and β-cyanoalanine synthase activity peaked 36 hours after wounding. The rate of cyanide evolution from the cut sections of apple flesh was 2.67±0.41ng/g F.W./hr (1.71+0.26pmol/g F.W./min).
Concomitant changes in the ACC and CN^- content, rate of ethylene production and β-cyanoalanine synthase activity were also observed during the ripening process of fruits of Japanese persimmon and kiwifruit stored at 25°C.
The development of cyanide-resistant respiration in ripening or wounded friut tissues seemed to be closely related to the increase in β-cyanoalanine synthase activity.