Effects of inhibitors and glucose on cytochrome and alternative respiration and on adenylate energy charge (AEC) in glucose-starved
Chlorella protothecoides
were investigated. 1 mmol/L azide (NaN
3), which immediately caused an increase of O
2 uptake by inhibiting the cytochrome pathway and stimulating alternative respiration, resulted in a decrease of AEC value from 0.83 to 0.34 within 3 minutes. When 1 mmol/L salicylhydroxamic acid (SHAM) was added into the cell suspension, there was no apparent variation in AEC. Adding NaN
3 and SHAM together into cell suspension to inhibit both cytochrome and alternative pathways showed a same change of AEC as that of adding NaN
3 alone. When 2.0 mmol/L of glucose was added to a suspension of glucose-starved cells, the O
2 uptake rate was immediately stimulated from 0.81 up to 1.34 ] mmol/L O
2 ·min
-1 ·(mL PCV)
-1 ] . The respiration stimulated by glucose could be inhibited about 20% by adding 1 mmol/L SHAM. It was found by titration with SHAM in the absence and presence of NaN
3 that 53% of O
2 uptake went through the cytochrome pathway and 45% of the alternate pathway was operational in enhanced respiration. It implied that induced operation of the alternative respiratory pathway probably resulted from the burst of the electron flux into the electron transport chain by glucose stimulation.
