A zinc-dependent lactate dehydrogenase in Euglena gracilis

Abstract

Intact cells of Euglena gracilis grown in a medium containing sufficient zinc oxidize lactate at high rates (400-800 [mu]l of oxygen consumed/hr. /mg of protein nitrogen). Zinc-deficient Euglena oxidizes lactate at a rate of about 40 [mu]l of oxy-gen/hr. The failure of lactate oxidation in zinc deficiency is due in part to decreased activities of D-lactate dehydrogenase. A manometric method is described for measuring lactate-dehydrogenase activity in Euglena homogenates or frozen and thawed cells.