Properties of Wheat Mitochondria. Study of Substrates, Cofactors and Inhibitors

Isolated mitochondria of wheat shoots oxidize α‐ ketoglutarate, DL‐malate succinate and NADH with good relative respiration control and ADP: O ratio. They have high affinity for α‐ketoglutarate and NADH as substrates and utilize malate and succinate with a respiration ratio of about one‐half of α‐ketoglutarate. The average ADP : O ratios approach the expected theoretical values, i.e. , 3.6 ± 0.2 for α‐ketoglutarate, 1.8 ± 0.2 for succinate, and 2.8 ± 0.2 for malate. The ADP: O ratio with NADH is 1.8 ± 0.2. The maximum coupling of oxidation and phosphorylation is obtained at concentrations of 10 m M , 2 m M , 10 m M and 8 m M for α‐ketoglutarate, NADH, malate and succinate, respectively. — Wheat mitochondria have little or no dependence on added cofactors. Mitochondria prepared by our procedure apparently retain sufficient amounts of endogenous cofactors required for NAD‐linked systems. FAD + is found to improve succinate oxidation. Cytochrome c does not have any significant effect on respiratory parameters of wheat mitochondria. — Wheat mitochondria are some ‐what resistant to DNP at 1.7 × 10 ‐5 M . Malonate seems to improve coupling of α‐ketoglutarate oxidation. Other Krebs cycle intermediates have been tested on three major substrates of TCA cycle, i.e. , α‐ketoglutarate, malate and succinate.