Mechanism  of Enzyme Action

 The action of enzymes is to lower  the activation energy  or threshold  of their substrates which. Therefore  become  activated and   react  with  the other reactants  .The  specific amino acid  sequence and molecular shape of the  enzyme  are of primary  importance in this function but its  mechanism is not yet properly under stood  ,The main  views  have been  expressed  t explain  this mechanism .

1. Lock and key or Template Hypothesis: Emil Fischer  1894  hypothesized  that each  enzyme molecule  has a specific and  rigid  active  site upon its surface .A reactant molecule having a matching  geometrical  configuration   only  can fit into this  active  site  of enzyme  like  a key fitting   into a lock forming an unstable enzyme substrate complex ,This  linkage actives the  substrate molecules  to react readily with  the other reactant of the  reaction

2. Induced fit Model Hypothesis: The  lock and key model has been  modified  by koshland 1971 and his co-workers  who  have suggested that the active silt  of an enzyme  molecule  is flexible. As  the specific  substrate molecule links with the  enzyme  molecule the latter undergoes conformation changes  so that the  fit  is improved the  reactive groups of enzyme  molecule move to their  proper sites.