Studies on dehydrogenase activities during amphibian metamorphosis

Abstract

The levels of activity of glutamic acid, lactic acid, glucose 6-phosphate, and malic acid dehydrogenases in prematamorphic tadpole liver and adult frog liver were determined. The level of glutamic acid dehydrogenase activity is six times higher in adult frog liver than in tadpole liver. Adult frog liver has slightly higher malic acid dehydrogenase, but lower glucose 6-phosphate and lactic acid dehydrogenase activities than tadpole liver. During thyroxine-induced metamorphosis (immersion of tadpoles in 2.6 · 10 −8 M thyroxine), the glutamic acid dehydrogenase activity of tadpole liver increased 150% after 20 days; lactic acid dehydrogenase and glucose 6-phosphate dehydrogenase activities decreased to 50–60% and to 75–80%, respectively, of the premetamorphic values. Tadpole and frog liver glutamic acid dehydrogenase is active with both DPN with the H 2O 2-generating system and 10 −6 M KI, for 2 or more minutes prior to addition of 131I, iodinating activity was destroyed (Table II). KI (10 −5 M) and tyrosine (10 −3 M) present during the incubation protected the enzyme (Table III).