Malonate and Cyanide Insensitivity in Relation to Respiratory Compensation in Potato Slices

Abstract

An attempt was made to distinguish whether when a tissue displays insensitivity to a respiratory inhibitor the respiration is in fact indifferent to the inhibitor, or whether inhibition is effected but masked by compensatory respiratory activity of another kind. The influence of malonate and of cyanide was observed on the extent and distribution of radioactivity among metabolic intermediates in malonate and in cyanide-resistant potato disks presented with glucose-U-C14. The results suggest that malonate resistance of potato disk respiration reflects inhibitor insensitivity, while cyanide resistance indicates the evocation of compensatory respiratory activity. It is suggested that the substrate for compensatory respiration differs from that for normal respiratory metabolism. Organic acids which become labeled when potato slices are incubated in solutions of radioactive glucose remain labeled when disks are removed therefrom and further incubated. Reasons have been offered for questioning that the labeled organic acids which persist with time are sequestered in the vacuole, although no alternative explanation has been suggested.