Serine Racemase from Oryza sativa L. : Regulation of Two Enzyme Activities and Structural Changes by Magnesium (II) Ion

Abstract

The serine racemase is a bifunctional enzyme that catalyzes a racemization and a dehydratation (α, β-elimination) of serine, and it has been found in various eukaryotes, such as human, mouse, fission yeast, cellular slime mold and plants. The serine racemase belongs to the fold-type II of the pyridoxal 5ʼ-phosphate (PLP) enzymes. We reported the clonig and expression of the serine racemase from Oryza sativa L. (SerR) and discovered the regulation mechanism of two enzyme reactions by Magnesium (II) ion (Mg²⁺). To examine the regulation mechanism of Mg²⁺, we tried to analyze the fluorescence quenching of tryptophan (Trp) residues in SerR by acrylamide. The result showed that the structure of SerR is distorted by the addition of Mg²⁺, and this structural change probably regulates the two enzyme activities.