Glyoxylate aminotransferases from wheat leaves

Abstract
Chromatographic studies were made of the following aminotransferases in crude, dialyzed extracts of wheat leaves (Triticum aestivum L. var. Selkirk): alanine: glyoxylate; aspartate: glyoxylate; glycine: 2-oxoglutarate (EC2.6.1.4); serine: glyoxylate; L-aspartate: 2-oxoglutarate (EC 2.6.1.1); L-alanine: 2-oxoglutarate (EC 2.6.1.2).After partial purification, the properties of serine: glyoxylate aminotransferase were studied in greater detail. This reaction proceeded in the forward direction to no more than one-half completion but no reverse reaction could be detected. The enzyme showed optimum activity at pH 8.2, and Km values of 9.0 × 10−4 M for serine and 2.5 × 10−4 M for glyoxylate were obtained. No clear requirement for the coenzyme pyridoxal phosphate or for metal ion participation could be shown but orthophosphate activated the enzyme when the latter was isolated in either Tris buffer or distilled water. Various aspects of glycine metabolism are discussed in relation to this and other work recently reported using wheat blades.