Kinetic behaviour of soluble invertases may be connected with the differential heat sensitivity of two wheat genotypes

Soluble acid and neutral invertases purified from the midmilky stage grains of a heat-susceptible (HD 2329) and a heat-tolerant (TDR-195) genotype of wheat (Triticum aestivum L.) showed marked differences in pH optima, Km and Vmax values. Both the invertases were more thermostable in TDR-195 because of inherent heat-tolerance ability of this genotype. Inhibition of enzyme activity by iodine and its regeneration by β-mercaptoethanol implied the involvement of sulphydryl groups for enzyme action. Inhibitory effect of sulphydryl group modifiers and various metal ions was much more pronounced in the susceptible genotype than in the tolerant genotype. Overall, it appears that the observed differences in thermal stability and kinetic behaviour of invertases may be connected to the differential heat sensitivity of the two genotypes studied.