Enzymes (isoenzyme system) as homeostatic mechanisms the isoenzyme (ADA2) of adenosine deaminase of human monocytes-macrophages as a regulator of the 2'deoxyadenosine.

Regarding homeostatic mechanisms in the enzyme (isoenzymes) and substrate system we show through a simulation model obtained by STELLA II software that: (i) a pair of isoenzymes (Is1 and Is2) that have different affinity for the substrate (Is2 affinity < Is1 affinity), can constitute an efficient homeostatic mechanism: by varying the relative concentration of the isoenzymes in the system, the levels of the substrate can be controlled; (ii) the isoenzymes ADA1 and ADA2 of adenosine deaminase (ADA) that have different affinity for the substrate 2'deoxyadenosine (ADA2 has very weak affinity for 2'deoxyadenosine) constitute, inside human Monocytes-Macrophages, a homeostatic mechanism that assures an up-regulation of 2'deoxyadenosine and a down-regulation of a second substrate (adenosine) for which the affinity of the two isoenzymes is similar.