AN NAD-SPECIFIC GLUTAMATE-DEHYDROGENASE FROM CYANOBACTERIA - IDENTIFICATION AND PROPERTIES

The unicellular cyanobacterium Synechocystis sp. PCC 6803 presents a hexameric NAD-specific glutamate dehydrogenase with a molecular mass of 295 kDa. The enzyme differs from the NADP-glutamate dehydrogenase found in the same strain and is coded by a different gene. NAD-glutamate dehydrogenase shows a high coenzyme specificity, catalyzes preferentially glutamate formation and presents K(m) values for ammonium, NADH and 2-oxoglutarate of 4.5 mM, 50-mu-M and 1.8 mM respectively. An animating role for the enzyme is discussed.