FIG 3.

Terrestrial pectin is de-esterified by PsCE8, PsCE10, and PsCE12. (A and B) The ability of the three putative pectin esterases to liberate methanol (A) or acetic acid (B) from citrus pectin was tested in enzyme-coupled assays. The weak acetylesterase activity of PsCE8 was confirmed at two enzyme concentrations (2 μM and 10 μM); the apparent weak methylesterase activity of PsCE10 seen in panel A was not increased in magnitude at 10 μM enzyme (data not shown), so it appears to be artifactual. The symbol legend applies to both panels. (C) The rate of unsaturated oligouronate production from pectin by PsPL1 was monitored at 230 nm in the presence and absence of PsCE8, PsCE10, and PsCE12 (indicated by + and −). Asterisks indicate statistically significant differences between enzyme combinations and the PsPL1-only sample as determined by a one-way analysis of variance (ANOVA) with Bonferroni posttest (****, P ≤ 0.0001; ns, P > 0.05). In all panels, data shown are the mean of three replicates and error bars represent the SEM.