The statement that enzymes are highly specific means that reactions involving specific substrates are catalyzed by specific enzymes.
Enzymes are biological catalysts that speed up chemical reactions in living organisms. Each enzyme has a unique structure that fits a specific substrate, much like a key fits into a particular lock. This specificity arises from the unique arrangement of amino acids in the enzyme, which creates an active site that accommodates only certain substrates.
For example, the enzyme lactase only catalyzes the breakdown of lactose into glucose and galactose. Other enzymes, such as amylase or lipase, catalyze entirely different reactions with completely different substrates. Thus, this specificity ensures that cellular reactions occur in an orderly and efficient manner without interference from unrelated compounds.