The kinetics and thermal stability of phosphogluco-isomerase isozymes of ryegrasses (Lolium spp.)

The Michaelis constants (K_m) and activation energies (E_a) for allozymes of cytosolic phosphogluco-isomerase (PGI-2; EC 5.3.1.9) from ryegrasses ( Lolium perenne L., Lolium multiflorum Lam. and interspecific hybrids) have been investigated. Differences were found between the allelic isozymes, but intra-allelic variations were at least as large. The thermal stability of the isozymes also varied, with the most commonly occurring form (the b -allozyme) having the highest stability at 50°C. Some possible explanations for these findings are discussed and the implications for plant breeders outlined.