Figure 8.

Experiment-2 of the gastric acidic pH effects (pH = 3.5) (with describing model parameter estimates $\pm \mathrm{SE})$ on GH5-p4818Cel5_2A activity over a 5-h period after the gastric pH buffer being mixed with the crude GH5-p4818Cel5_2A enzyme preparation prior to further incubation for measuring cellulase activity with the carboxymethyl cellulose (CMC) substrate buffer in presence of dithiothreitol (DTT) (5 mM) and N₂ gas purging for 15 min at 37 °C. (A) Quadratic plot of the inhibition kinetic relationship between GH5-p4818Cel5_2A activity (v, mean $\pm \mathrm{SE},\mathrm{n}=12\mathrm{at}\mathrm{each}\mathrm{time}\mathrm{point},$ nmol/mg protein•min) and incubation time (t, h) under the gastric pH 3.5 condition according to the quadratic response model established as: $\mathrm{Y}=86.308\left(\pm ,6.209\right)+19.458\left(\pm ,5.703\right)x-3.278(\pm 1.068)x^2$, P < 0.0001 for intercept; P = 0.001 for the linear parameter estimate; and P = 0.003 for the quadratic parameter estimate; ${\mathrm{R}}^2=0.29$, n = 84; and alternatively, according to the linear response model established as $\mathrm{y}=99.305\left(\pm ,4.771\right)+2.638\left(\pm ,1.658\right)\mathrm{x}$, P < 0.0001 for the intercept; and P = 0.116 for the slope; ${\mathrm{r}}^2=0.207$, n = 84; (B) Quadratic plot of the inhibition kinetic relationship between the relative GH5-p4818Cel5_2A activity (v, mean $\pm \mathrm{SE},\mathrm{n}=12\mathrm{at}\mathrm{each}\mathrm{time}\mathrm{point},$ % of the control group measured at I_C of 100.000 ± 7.523 at 0-min exposure to the gastric pH 3.5 incubation) and incubation time (t, h) under the gastric pH-3.5 condition according to the quadratic response model established as: $\mathrm{Y}=99.245\left(\pm ,7.139\right)+22.374\left(\pm ,6.558\right)x-3.769(\pm 1.228)x^2$, P < 0.0001 for intercept; P = 0.001 for the linear parameter estimate; and P = 0.003 for the quadratic parameter estimate; ${\mathrm{R}}^2=0.29$, n = 84; and alternatively, according to the linear response model established as $\mathrm{y}=114.2\left(\pm ,5.486\right)$, P < 0.0001 for the intercept; and P = 0.116 for the slope, ${\mathrm{r}}^2=0.207$, n = 84; (C) the Eadie-Hofstee linear plot between the GH5-p4818Cel5_2A enzyme activity (v, mean $\pm \mathrm{SE},\mathrm{n}=12\mathrm{at}\mathrm{each}\mathrm{data}\mathrm{point},$ nmol/mg protein•min) and the v/t ratio established as $\mathrm{y}=98.265\left(\pm ,5.708\right)+0.200\left(\pm ,0.096\right)\mathrm{x}$, P < 0.0001; for the intercept and P = 0.041 for the slope, ${\mathrm{r}}^2=0.059$, n = 72; and (D) the Eadie-Hofstee linear plot between the relative GH5-p4818Cel5_2A enzyme activity (v, mean $\pm \mathrm{SE},\mathrm{n}=12\mathrm{at}\mathrm{each}\mathrm{data}\mathrm{point},$ % of the control group measured at I_C of 100.000 ± 7.523) at 0-min exposure to the gastric pH 3.5 incubation) and the v/t ratio established as $\mathrm{y}=113.000\left(\pm ,6.563\right)+0.200\left(\pm ,0.096\right)\mathrm{x}$, P < 0.0001 for the intercept; and P = 0.041 for the slope, ${\mathrm{r}}^2=0.05$, n = 72.