title: Occurrence of thermolabile and regulatory NAD-linked glutamate dehydrogenase in Pseudomonas fluorescens.
abstract: NAD-linked glutamate dehydrogeanse [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 degrees 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.
mesh_terms: D005969:Glutamate Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D009243:NAD; D009249:NADP; D011551:Pseudomonas fluorescens / Q000201:enzymology*; D013696:Temperature
chemical_list: D007527:Isoenzymes; D009243:NAD; D009249:NADP; D005969:Glutamate Dehydrogenase