Sometimes more than one enzyme can catalyze the same reaction in parallel; this can allow more complex regulation: with, for example, a low constant activity provided by one enzyme but an inducible high activity from a second enzyme.
Nogle gange kan mere end ét enzym katalysere den samme reaktion parallelt, hvilket tillader mere kompleks regulering: for eksempel kan ét enzym agere med en lav konstant aktivitet, mens et andet enzym agerer med høj aktivitet, hvis fremkaldt.