Partial Purification and Characterization of Acid Invertase from the Fresh and Stale Sugarcane Juice

Abstract

Soluble acid invertases from the fresh and stale cane juice of variety CoJ83 were purified by fractional precipitation with ammonium sulphate and ion exchange chromatography with DEAE- cellulose. Three isoforms of acid invertase were identified in juice of fresh cane and four isoforms of enzyme were found in juice of stale cane. The isoforms obtained were characterized for their kinetic parameters. Optimum pH and optimum temperature range of isoforms from fresh cane juice were 4.5–5.0 and 35–45°C, however isoforms of invertase from juice of stale cane were having optimum pH of 4.0–4.5 and optimum temperature 40–55°C. Isoforms identified from juice of stale canes were kinetically more efficient in comparison to isoforms identified from juice of fresh canes, as they were having higher Vmax/Km values than isoforms from fresh cane juice. MnCl2 inhibited the soluble acid invertase isoforms of fresh cane completely, but it was unable to inhibit completely the enzyme isoforms of juice of stale cane. ZnCl2, NiCl2, KCl, sodium metasilicate, sodium lauryl sulphate and KMnO4 inhibited the activity of different invertase isoforms in both fresh and stale cane juice, but this inhibition percent was relatively less in stale cane enzyme isoforms as compared to enzyme isoforms from juice of fresh cane. This points to the existence of structural and conformational differences among invertase isoforms in juice of fresh and stale cane.