Saccharopine, an intermediate of the aminoadipic acid pathway of lysine biosynthesis. IV. Saccharopine dehydrogenase.

Two pathways of lysine biosynthesis are known to exist in nature. The diaminopimelic acid pathway, studied in detail in Escherichia coli (l), is the route of lysine biosynthesis in bacteria, certain lower fungi, algae, and higher plants (2). In other classes of lower fungi, in higher fungi, and in Euglena, lysine is synthesized in a different manner, involving the intermediate cu-aminoadipic acid (2). Recent investigations in our laboratory have been aimed at characterizing the steps in the conversion of Lu-aminoadipic acid to lysine. In the initial reaction(s) in yeast, cr-aminoadipate is reduced to cr-aminoadipic-6-semialdehyde (3, 4). The discovery that saccharopine, e-N-(glutaryl)-2)lysine,