The Effect of Fructose as an Inhibitor in the Hydrolysis of Lactose
IP Suriyamas
Secondary trackOriginal researchBiologyOct 20, 2026English
This study investigated the inhibitory effect of fructose concentration on lactase-mediated hydrolysis of o-nitrophenyl-β-D-galactopyranoside (ONPG), a synthetic substrate used to assess lactase activity. Six fructose concentrations (0, 20, 40, 60, 80, and 100 mM) were tested under controlled conditions of pH 7.0 and 37°C, with five trials conducted per concentration. Following a 20-minute incubation period, enzymatic activity was quantified using spectrophotometric absorbance at 420 nm to measure the formation of o-nitrophenol. Results demonstrated a strong negative relationship between fructose concentration and ONPG hydrolysis, with mean absorbance decreasing from 0.147 AU in the control group to 0.065 AU at 100 mM fructose, representing a 55.8% reduction. A one-way ANOVA revealed statistically significant differences between treatment groups (p < 0.001). These findings suggest that increasing fructose concentration significantly reduces lactase activity under the experimental conditions, consistent with previously documented competitive inhibition of lactase by fructose. However, further kinetic analysis is necessary to establish the specific inhibition mechanism. Overall, this investigation provides experimental evidence of concentration-dependent inhibition of lactase activity by fructose, contributing to the understanding of how dietary sugars may influence enzymatic carbohydrate hydrolysis.