Biochemical investigations
Biochemical investigation encompasses a screening of the complete metabolic function by measuring the volume of various mitochondrial substrates. Unfrozen tissue is required for this. This investigation also allows the detection of dysfunctions involving transportation via the mitochondrial membranes (e.g. mitochondrial phosphate carriers) which would otherwise remain undiscovered.
Functional investigation of a patient with defective pyruvate oxidation:
| [nmol/h/mg/mUnit citrate synthase] |
Patient |
Normal range |
| |
|
|
| [1-14C]pyruvate+malate |
0,44 |
1,54 - 3,55 |
| [1-14C]pyruvate+carnitine |
0,42 |
1,65 - 3,66 |
| [U-14C]malate+pyruvate+malonate |
0,58 |
1,56 - 3,87 |
| [U-14C]malate+acetylcarnitine+malonate |
1,13 |
1,16 - 2,82 |
| [U-14C]malate+acetylcarnitine+arsenite |
0,68 |
0,57 - 1,52 |
| [1,4-14C]succinate+acetylcarnitine |
0,85 |
0,90 - 2.06 |
In addition, a quantification of individual enzymes involved in oxidative phosphorylation and pyruvate oxidation is carried out. Biochemical investigation often enables the affected enzyme to be detected and is therefore usually a pre-requisite for a molecular genetic investigation.
Enzyme activities of a patient:
| mUnits/mg Protein |
Patient |
Normal range |
| |
|
|
| citrate synthase |
511 |
150 - 325 |
| complex I |
10 |
28 - 76 |
| complex I+II |
78 |
64 - 218 |
| complex II |
128 |
39 - 102 |
| complex II+III |
330 |
93 - 180 |
| complex III |
89 |
426 - 762 |
| cytochrome c oxidase |
76 |
452 - 889 |
| oligomycin-sens. ATPase |
131 |
70 - 397 |
| pyruvate dehydrogenase |
8,8 |
6,1 - 19,8 |
