Process Biochemistry, Vol.49, No.9, 1480-1487, 2014
Effect of deglycosylation on the properties of thermophilic invertase purified from the yeast Candida guilliermondii MpIIIa
Invertase from Candida guilliermondii MpIIIa was purified and biochemically characterized. The purified enzyme (INV3a-N) is a glycoprotein with a carbohydrate composition comprising nearly 74% of its total molecular weight (MW) and specific activity of 82,027 U/mg of protein. The enzyme displayed optimal activity at pH 5.0 and 65 degrees C. The Km and V-max values for INV3a-N were 0.104 mM and 10.9 mu mol/min/mg of protein, respectively, using sucrose as the substrate. The enzyme retained 50% and 20% of its maximal activity after 168 h and 30 days, respectively, at 50 degrees C. INV3a-N was fully active at sucrose concentrations of 400 mM and the activity of the enzyme dropped slowly at higher substrate concentration. Interestingly, the deglycosylated form of INV3a-N (INV3a-D) displayed 76-92% lower thermostability than that of INV3a-N at all temperatures assayed (50-70 degrees C), and was inhibited at sucrose concentrations of 200 mM. Findings here indicate glycosylation plays an important role, not only in the thermostability of INV3a-N, but also in the inhibition of the enzyme by sucrose. Since the enzyme is active at high sucrose concentrations, INV3a-N may be considered a suitable candidate for numerous industrial applications involving substrates with high sugar content or for improvement of ethanol production from cane molasses. (C) 2014 Elsevier Ltd. All rights reserved.