Occurrence of Thermolabile and Regulatory NAD-Linked Glutamate Dehydrogenase in Pseudomonas fluorescens

抄録

NAD-linked glutamate dehydrogenase [EC 1. 4. 1. 2] was detected together with NADP-linked glutamate dehydrogenase [EC 1. 4. 1. 4] and aspartase [EC 4. 3. 1. 1] in Pseudomonas fluorescens cells. The three enzymes were distinctly separated by DEAE-Sephadex column chromatography. The NAD-linked enzyme was extremely thermolabile and was rapidly inactivated even at temperatures as low as 35-40°C. The combined addition of NAD⁺ and glutamate, however, effectively stabilized the enzyme. The glutamate saturation profile of the NAD-linked enzyme exhibited cooperativity with a Hill coefficient (n) of 1.4. ATP inhibited the enzyme in an allosteric manner, increasing the n value to 2.2. These results suggest a novel type of metabolic regulation shared by the three enzymes in the biosynthesis and catabolism of amino acids.