Table III.
Catabolism of Leu by mitochondrial extracts
| Additions/Omissions | Incubation Duration | α-KIC | IV-CoA | MC-CoA |
|---|---|---|---|---|
| h | dpm (×103)/mg protein | |||
| None | 0.33 | 256.4 (+45.1) | NDa | ND |
| 1 | 585.3 (+102.9) | 19.7 (+2.3) | ND | |
| 2 | 1303.2 (+229.1) | 110.5 (+13.0) | ND | |
| 4 | 697.6 (+122.7) | 426.5 (+50.2) | 8.6 (+4.2) | |
| 6 | 362.1 (+63.7) | 508.6 (+59.8) | 29.9 (+14.4) | |
| −α-KG | 2 | 89.4 (+15.7) | ND | ND |
| −CoA | 2 | 1214.7 (+213.6) | ND | ND |
| +1 mm α-KIC | 2 | 1099.0 (+193.2) | ND | ND |
| 4 | 1835.0 (+322.6) | ND | ND | |
| 6 | 2270.3 (+399.1) | ND | ND | |
| +Avidin | 2 | 936.8 (+164.7) | 154.3 (+18.2) | ND |
| 4 | 800.7 (+139.9) | 420.6 (+49.5) | 51.4 (+24.7) | |
| 6 | 602.4 (+105.9) | 436.8 (+51.4) | 71.7 (+34.5) | |
Mitochondrial extracts were incubated with [U-14C]Leu and cofactors for various lengths of time and the resulting radioactive products were analyzed by HPLC. Additional reactions were also conducted without added α-ketoglutarate (α-KG) or CoA, or with the addition of 1 mm nonradioactive α-KIC or 10 μg of avidin. α-KG is required for the transamination of Leu; CoA is required for the decarboxylation and activation of α-KIC in the BCKDH reaction; nonradioactive α-KIC inhibits further metabolism of α-[14C]KIC by competition; and avidin inhibits MCCase. se values are reported as in Table II.
a
ND, Not detected.