= Substrate analogue
A <substrate analogue> is a <molecule> designed or recognized as resembling an <enzyme>'s <substrate> in features relevant to binding or reaction. Resemblance may involve molecular shape, <electric charge> or the arrangement of reactive groups. An analogue need not reproduce every property of the natural <substrate>: it may bind without undergoing the same reaction, react at a different rate or stabilize a useful experimental complex.
For a conceptual example, suppose a natural <substrate> is recognized through two binding groups and transformed at a third group. An analogue retaining the recognition groups but replacing the reactive group could reveal how the <active site> holds the <substrate>. Observing binding would answer a recognition question; it would not establish the natural reaction rate. Nor does the word analogue alone guarantee <competitive inhibition>: that requires evidence about how the compound affects the <enzyme> under the tested conditions.
In a 2000 <ribosome> study, structures of the <large ribosomal subunit> bound to two <substrate analogues> located the <peptidyl transferase center>. Conserved <23S ribosomal RNA> contacted the analogues, providing evidence about the chemical environment for <peptide bond> synthesis.<The structural basis of ribosome activity in peptide bond synthesis by Poul Nissen and others>[Abstract, analogue-bound structures and conserved RNA contacts]{ref} The experimental value lies in making a normally transient arrangement accessible to structural measurement; interpreting the natural <substrate> still requires attention to what the analogue preserves and changes.
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