Biochemical Study on the Kinetic Properties of the Invertase Produced by Saccharomyces Cerevisiae

Abstract

Invertases are enzymes that hydrolyze sucrose to produce an equimolar mixture of glucose and fructose, which is of interest for various industrial applications. The present study aimed to produce invertase by Saccharomyces cerevisiae isolated from Baker’s yeast and grape samples using the standardize technique. The enzyme activity was characterized with some parameters like pH, temperature, metal ions, kinetic parameters and inhibitors (fructose, glucose and copper (II) sulfate). Spectrophotometric methods were used to study enzyme kinetics and to determine the factors affecting enzyme activity. The optimum activity was recorded at 55˚C for both invertases. The optimum activity was at pH 6.0 for Baker’s yeast invertase and at pH 10 for grape invertase. From Lineweaver-Burk Plot, Vmax was found to be 24.39 ± 2.44 nmol/min/mg protein and the Km approximately 0.860 ± 0.04 mM for Baker's yeast invertase but in case of grape invertase, Vmax was 23.25 ± 3.14 nmol/min/mg protein and the Km approximately1.243 ± 0.07 mM. Enzyme activity was increased in the presence of 5 mM Ca+2 ions for Baker’s yeast, whereas showed the maximum activity at 5 mM Mg+2 ions in case of grape fruit invertase. Using sucrose as substrate, the Kcat, Kcat/Km and Ks values were 0.28 ± 0.02 min-1, 0.325 ± 0.03 mM-1 min-1 and 27.03 ± 5.24 ml/min/mg protein for Baker’s yeast invertase activity, whereas were 0.56 ± 0.008 min-1, 0.045 ± 0.003 mM-1 min-1 and 24.39 ± 7.11 ml/min/mg protein for grape invertase values. In conclusion, the S. cerevisiae isolated from grape fruits was more potent for invertase production in comparable with that isolated from Baker’s yeast.