Figure 9.

Experiment-2 of the gastric acidic pH and pepsin (274 U/mL) effects (with describing model parameter estimates $\pm \mathrm{SE})$ on GH5-tCel5A1 activity over a 5-h period after the gastric pH and pepsin buffer being mixed with the crude GH5-tCel5A1 enzyme preparation for incubation at the resulting mixture pH = 3.5 and pepsin at 274 U/mL 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) Exponential plot of the inhibition kinetic relationship between the GH5-tCel5A1 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 and pepsin (274 U/mL) conditions established according to the exponential response model as: $\mathrm{Y}=23.156\left(\pm ,2.157\right){\mathrm{e}}^{(-\mathrm{x})}$, P < 0.0001 for the initial residual tCel5A1 activity estimate; and P = 0.228 for the rate constant estimate; ${\mathrm{R}}^2=0.072$, n = 84; and alternatively, according to the linear response model established as $\mathrm{y}=23.084\left(\pm ,2.254\right)+0.949\left(\pm ,0.783\right)\mathrm{x}$, P < 0.0001 for the intercept; and P = 0.229 for the slope, ${\mathrm{r}}^2=0.072$, n = 84; (B) Exponential plot of the inhibition kinetic relationship between the relative GH5-tCel5A1 activity (v, mean $\pm \mathrm{SE},\mathrm{n}=12\mathrm{at}\mathrm{each}\mathrm{time}\mathrm{point},$ % of the control group measured (100.000 ± 19.716) at the 0-min exposure to the gastric pH-3.5 and pepsin-274 U/mL incubation) and incubation time (t, h) under the gastric pH 3.5 and pepsin (274 U/mL) conditions according to the exponential response model established as: $\mathrm{Y}=115.000\left(\pm ,10.715\right){\mathrm{e}}^{(\mathrm{x})}$, P < 0.0001 for the initial residual GH5-tCel5A1 activity estimate; and P = 0.228 for the rate constant estimate, ${\mathrm{R}}^2=0.07$, n = 84; and alternatively, according to the linear response model established as $\mathrm{y}=114.600\left(\pm ,11.193\right)+4.711\left(\pm ,3.891\right)x$, P < 0.0001 for the intercept; and P = 0.229 for the slope, ${\mathrm{r}}^2=0.072$, n = 84; (C) the Eadie-Hofstee linear plot between the tCel5A1 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 $\mathrm{y}=17.432\left(\pm ,1.455\right)+0.703\left(\pm ,0.086\right)\mathrm{x}$, P < 0.0001 for all parameter estimates, ${\mathrm{r}}^2=0.551$, n = 72; and (D) the Eadie-Hofstee linear plot between the relative GH5-tCel5A1 enzyme activity (v, mean $\pm \mathrm{SE},\mathrm{n}=12\mathrm{at}\mathrm{each}\mathrm{data}\mathrm{point},$ % of the control group measured (100.000 ± 19.716) at the 0-min exposure to the gastric pH-3.5 and pepsin-274 U/mL incubation) and the v/t ratio established as $\mathrm{y}=86.577\left(\pm ,7.228\right)+0.703\left(\pm ,0.086\right)\mathrm{x}$, P < 0.0001 for all parameter estimates; ${\mathrm{r}}^2=0.551$, n = 72.