1. LDH + pyruvate + NADH ---> LDH-pyruvate-NADH-complex 2. reacting of NADH + PYR in the complex to NAD + L-lactate 3. LDH-L-lactate-NAD + -complex ---> LDH + L-lactate + NAD + Note that while the LDH is a catalyst of the overall reaction, once we drill down into sub-reaction steps, the catalyst becomes a reactant and finally a product. In most enzyme mechanisms the binding of ligands happens stepwise with specific conformation changes, all of which, if known or predicted, can be represented by these 3D molfiles of the critical components in additional intermediary steps. Of course, 2D molfiles can also be used if the exact coordinates are not known and the Reaction SPL author wants to visualize only schematic reaction mechanisms.