ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 86 Number 3
Kinetic properties of soluble acid invertase from the leaf blade of sugarcane cultivars varying in sucrose content. (91)
Kinetic properties of soluble acid invertase extracted from leaf blades of three sugarcane cultivars viz; Co 89003 (high sugar and early maturing), CoJ 86 (medium sugar and early maturing) and CoS 96260 (low sugar and mid maturing) were studied at tillering stage. The enzyme showed its maximum activity at pH 5.5 and temperature 45 degree C in all three cultivars. Mercuric chloride, manganese chloride and ammonium molybdate strongly inhibited the activity of enzyme in all three cultivars. Inhibition by cobalt chloride, calcium chloride and magnesium chloride was mild. Potassium chloride stimulated the enzyme significantly in CoS 96260. From the effect of temperature on Km and Vmax values, the energy of activation (Ea), enthalpy change (delta H), free energy change (delta G) and entropy change (delta S) were observed to be 76.6 kJmol-1, -34.9 kJmol-1, 9.7 kJmol-1 and 79.1 JK-1mol-1 in Co 89003. The corresponding values of these thermodynamic parameters, were 63.2 kJmol-1, 47.9 kJmol-1, 7.8 kJmol-1 and 126.0 JK-1mol-1 in CoJ 86 and 54.8 kJmol-1,54.8 kJmol-1, 9.5 kJmol-1 and 142.1 JK-1 mol-1 in CoS 96260. Soluble acid invertase from CoS 96260 showed a higher Vmax/Km value than the other two cultivars and thus was kinetically more efficient in sucrose hydrolysis.
Keywords: Invertase; sucrose accumulation; sugarcane; leaf blade