when either mn2+ , mg2+ , ca2+ , or co2+ was added to the relaxed ( divalent cation-free ) enzyme at saturated concentration , each produced a similar uv-difference spectrum of the enzyme , indicating that the conformational states induced by these cations are similar with respect to the polarity of the microenvironment surrounding the tyrosyl and tryptophanyl groups of the enzyme .
C0007448
divalent cation
C0007447
cations