Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The determining way of regulation of proline biosynthesis in plants at normal and low temperatures has been discovered. The first enzyme of the biosynthetic pathway, allosteric glutamate kinase (GK 1), is very active at low temperatures (0°, -20°C). In the normal temperature range the biosynthesis of proline is controlled by inhibition of GK 1 through feedback by L-proline (I₅₀ = 80μmol/l, I₁₀₀ = 50mmol/l). At low temperatures the inhibition switches over into allosteric activation and the biosynthesis of proline is started. It is a new type of instantaneous change of central regulation of the enzyme with change of ecology. In a range of temperature ADP is only a partial allosteric inhibitor of GK 1. L-Proline, ADP and low temperature bring about complex heterotropic cooperatives in GK 1, which are demonstrated by changes in the relation {v_o; [L-Glu]}. A hypothetical scheme of central regulation of proline-inhibitable glutamate kinase by L-proline with changes of temperature and concentration of salts has been worked out.