Fig. 4.

Abstract syntax tree for an enzymatic rate law for non-modulated unireactant enzymes (SBO:0000326). This tree has been constructed for the phosphoglucomutasereaction in model iJO1366 [69], in which \textsc{d}-glucose1-phosphate (g1p) is reversibly converted to \textsc{d}-glucose6-phosphate (g6p). The program internally constructs all equations in form of syntax trees, which can contain references to objects in the SBML document. In this example, the tree contains the parameters v _m+ and v _m− for the forward and reverse maximal reaction velocity (both in mol ·s ⁻¹), K _M1 and K _M2 for the Michaelis constants of the reactant and product (both in mol), the plain numerical value 1 (dimensionless in SBML Level 3, unit undefined for earlier versions of SBML), as well as references to the species g1p and g6p (both in mol). All internal nodes represent mathematical operators