Cold acclimation of wheat (Triticum aestivum): Properties of enzymes involved in proline metabolism

Two cultivars of wheat ( Triticum aestivum L.), a winter wheat, Kharkov, and a spring wheat, Glenlea, were acclimated under controlled conditions at 2 temperatures, 5°C and 25°C with a 12‐h photoperiod. Water content, protein and proline concentrations were determined. Enzymatic properties (activity and apparent energy of activation) were investigated for enzymatic systems involved in 2 pathways of proline metabolism, the glutamic acid and ornithine pathways. Four enzymes were studied, proline dehydrogenase (PDH, EC 1.5.1.2), glutamate dehydrogenase (GDH, EC 1.4.1.2‐4), glutamine synthetase (GS, EC 6.3.1.2) and ornithine transaminase (OT, EC 2.6.1.13). Cold acclimation led to an accumulation of proline, a decrease in water content and an increase in soluble protein, especially in winter wheat. For both cultivars, cold acclimation modulated enzyme properties of PDH and GDH. Increased activities of GS and OT were observed as a result of cold acclimation in both cultivars, with the greatest increase in Kharkov. The apparent energy of activation of these 2 enzymes decreased, particularly for Kharkov, which accumulated proline in cold conditions.