Sensitivity to drying in vitro of enzymes in mitochondrial subfractions from Vicia faba seed

In order to investigate the persistence of membrane and matrix functions following desiccation, enzymic activities were studied in Vicia faba L. seed mitochondrial subfractions subjected to drying and rehydration in vitro. Mitochondria were prepared after 0, 12 and 24 h of seed imbibition. These were fractionated into inner membranes ("submitochondrial particles"), outer membranes (12 and 24 h only) and the soluble matrix. Enzyme activities associated with the inner membrane and matrix were found to increase several-fold during the first 12 h of imbibition. The two matrix enzymes examined, malate dehydrogenase and glutamate dehydrogenase, were insensitive to in vitro drying at all stages of imbibition. The membrane-bound activities from 12 h and 24 h imbibed material, antimycin A-sensitive NADH: cytochrome c oxidoreductase and (F_o-F₁)-ATPase of the inner membrane and antimycin A-insensitive NADH: cytochrome c oxidoreductase of the outer membrane, were moderately sensitive to dehydration. The F₁-ATPase solubilized from the inner membrane (F_o-F₁) complex was much less sensitive to drying, provided this was done at room temperature.
Mitochondria posessing their outer membranes could not be prepared from dry seed. The antimycin A-sensitive NADH: cytochrome c oxidoreductase from inner mitochondrial membranes of unimbibed seed was extremely sensitive to desiccation in vitro, about 75 to 80% of the activity being lost. This loss could be somewhat reduced by addition of glycerol or sucrose before drying.
It is concluded that uncontrolled desiccation results in major damage to some of the membrane-bound enzymic systems in mitochondria, whereas activities in the soluble fraction are remarkably tolerant of desiccation.