Description
The ATP Profile determines the total ATP production and allows for a quantitative comparison of the cells’ energy engines – mitochondria and glycolysis – in a basal state.
The ATP Profile consists of the following markers:
- Total adenosine triphosphate (ATP)
- Mitochondrial ATP capacity
- Glycolytic ATP capacity
- Reserve ATP capacity
a) Total ATP
This is the quantity of ATP that the cells produce at rest via both mitochondrial and non-mitochondrial pathways. Total ATP is all the adenosine triphosphate (our cells’ energy currency) available to the cell. This makes it possible to assess the relative performance of mitochondrial respiration (mitochondrial ATP capacity) versus anaerobic glycolysis (glycolytic ATP capacity).
b) Mitochondrial ATP capacity
“Mitochondrial ATP capacity” measures the capacity to synthesise adenosine triphosphate (ATP) in the patient’s mitochondria in a defined basal state. This is calculated by determining the absolute ATP production that is inhibited by addition of the ATP synthase inhibitor oligomycin (see figure above). Mitochondrial-generated ATP, if production is functioning smoothly, has a very high harvest: ~34 ATP from one molecule of glucose, and far more from fats (e.g., ~ 146 ATP from one molecule of oleic acid). The metric is given as both a percentage and in femtomoles/cell. Lower than optimal ATP capacity suggests various possible dysfunctions.
c) Glycolytic ATP capacity
ATP can also be produced in the cytosol, outside the mitochondria (though still inside the cell). This is produced largely from glucose, and the amount of ATP per molecule of glucose is very low (just 2 ATP per molecule of glucose). This parameter measures the glycolytic capacity for ATP production: the maximum quantity of ATP that the cells are able to produce at rest via non-mitochondrial pathways, i.e. anaerobic glycolysis. This makes it possible to assess the relative performance of anaerobic glycolysis versus mitochondrial respiration. This metric, again, is expressed as a percentage as well as in femtomoles/cell.
d) Reserve ATP capacity
ATP synthesis is generally presumed to be coupled almost entirely to two metabolic processes: oxidative phosphorylation and glycolysis. There is however another essential metabolic process that interconverts the three adenine nucleotides (ATP, ADP and AMP) using adenylate kinase according to metabolic needs. Adenylate kinase catalyses a reversible reaction: 2 ADP > ATP + AMP. This is a vital factor in regulating the energy charge in cells, providing an open system able to accept, store and supply energy to cells as needed. The marker “Reserve ATP capacity” indicates how dynamically the cell is able to perform this catalytic interconversion.