Renal glutaminase in postnatal and adult rats

Properties of renal phosphate-dependent glutaminase (EC 3.5.1.2), assayed in tissue homogenates, were compared in adult, 2-week-old, and newborn rats. Vmax, Km glutamine, pH optimum, inhibition by glutamate, activation by phosphate, intracellular distribution, and the possible presence of activators or inhibitors were examined. Although Vmax increased threefold during postnatal development, no major differences in the properties of the enzyme at the three stages of development were noted. It was concluded that the enzyme protein remains the same throughout development, both in biochemical properties and intracellular location, but that more of it is accumulated or is converted to an active state as the kidney matures.