Properties of a new glyoxylate reductase from leaves

Abstract

A new glyoxylate reductase, which catalyses the reduction of glyoxylate to glycollate in the presence of NADPH2 has been demonstrated and separated to a large extent from the NADH2-linked glyoxylate reductase in both tobacco and spinach leaves. Unlike the NADH2-linked glyoxylate reductase of leaves, the new enzyme has a low Michaelis constant for glyoxylate, 0.13 m[image], and reacts only slowly with hydroxypyruvate. Pyruvate and oxaloacetate are not substrates. The kenetic properties and favorable equilibrium should make the NADPH2-linked glyoxylate reductase a useful reagent for the analytical estimation of glyoxylate. Together with NADH2[long dash]linked gly-oxylate reductase, both enzymes may be used to provide a convenient method for determining the concentration of NADPH2-and NADH2 in mixtures of the 2 dinucleotides. Although there is increasing evidence of the importance of glycollate and glyoxylate in the C metabolism and respiration of leaves, especially in sunlight, the physiological role of the glyoxylate reductases remains uncertain.