Why do enantiomers work differently in biochemical systems when they have the same physical and chemical properties? Also why do enantiomers that rotate plane polarised light to the left usually work.

the biomechanical systems are also enantiomeric.

 

The common example is an enzyme and its substrate. The enzyme is purely one enantiomer, and only one enantiomer of the substrate will fit into the active site of the enzyme.

 

It's a fact, and no-one really knows why, that ALL the complex molecules in living things are a single enantiomer