If the quasi-steady-state hypothesis is assumed in addition to BFEI hypothesis, then the complex concentration can be assumed to be in a stationary (steady) state according to the Briggs–Haldane hypothesis, and the GEBIK equations become
which are written in a form similar to the classical Micaelis-Menten equations for any substrate and product. Here, the equations also show that the various isotopologue and isotopomer substrates appear as competing species. Eqs. () for isotopic compositions, Eq. () for the fractionation factor and Eq. () for the enrichment factor equally applies to the GEBIK equations under the BFEI and QSS hypothesis.