EFFECT OF SALICYLHYDROXAMIC ACID ON RESPIRATION AND PEROXIDASE OXYGENASE ACTIVITY IN ALFALFA CELL-SUSPENSION CULTURE

We used polarographic technique and the respiration inhibitors cyanide , antimycin A, and salicylhydroxamic acid (SHA) to determine the invol vement of different terminal oxidases-cytochrome oxidase, mitochondria l alternative KCN-resistant oxidase (AO), and peroxidase-in oxygen upt ake by cell suspension culture of alfalfa (Medicago sativa L.). Despit e the presence of AO in mitochondria and peroxidase characterized by h igh oxygenase (NADH-oxidase) activity in cells, activity of the cytoch rome oxidase sector of the mitochondrial ETC made the main contributio n (up to 80%) to total oxygen uptake by the cell suspension. The corre sponding share of the other two oxidation systems did not exceed 20%, activity of peroxidase or the other (KCN-sensitive) cellular oxidase b eing dominant here. In the presence of exogenous NAD(P)H, SHA in a wid e range of concentrations is capable of playing the part of phenol as an activator of extracellular peroxidase, oxygen uptake increasing mul tifold in this case. On the other hand, high concentrations of SHA (20 -25 mM) strongly inhibited oxygen uptake associated with work of the c ytochrome oxidase sector of the mitochondrial electron transport chain (ETC). The authors discuss the possibility of using traditional respi ration inhibitors, SHA in particular, in research to determine the act ivity of terminal oxidases in cells, tissues, and organs of various pl ant objects.