Substrate specificity
Japanese: 基質特異性
The property by which an enzyme acts only on a specific substrate. The 'lock and key' relationship representing enzymatic precision.
Substrate specificity is the property by which an enzyme acts on only one particular substance. Protease breaks down protein but shows no reaction to starch. This precision is the key to controlling fermented food flavors.
An enzyme's active site has a shape that fits a specific substrate three-dimensionally. Emil Fischer's 'lock and key model' from 1894 is the origin of this concept. Today, the 'induced fit model'—where enzymes flexibly adjust their shape—is also recognized.
Because of substrate specificity, dozens of enzymes secreted by koji mold work independently at their respective stations without interfering. This parallel processing is the foundation of miso's complex flavor.