An enzyme-controlled reaction is often expressed in the following way:
molecules (orange rectangle) diffuse in [from the left, as in the equation] and bind with the active site
of the enzyme, which is complementary in shape (lock and key
concept). This forms the enzyme-substrate complex
. The change in shape and colour of the enzyme are a hint to the induced fit
model of enzyme action. In all hydrolysis reactions, water (represented by the small blue rectangle) participates in the breakdown
, with the release of products
(red and yellow squares), which diffuse away [to the right, as in the equation]. The process continues as long as there are substrate molecules to be converted, as the enzyme molecule (green) is unchanged at the end of the reaction.