Figure 7: Purified SeHAS synthesizing HA is resistant to inhibition by ZnCl2 or CuCl2. SeHAS was purified as described in Methods and, in a pretreatment, samples were incubated without (no HA; black circles), or with UDP-sugars for 5 (yellow triangles), 10 (green inverted triangles) or 15 (red squares) min, after which the indicated concentration of CuCl2 (A) or ZnCl2 (B) was added and the samples were incubated an additional 30 min under normal assay conditions to assess relative enzyme activities.