The Separation of Rat Liver Serine Dehydratase and Cystathionine Synthase

A compound derived from pyruvic acid and homocysteine has been isolated from reaction mixtures containing serine- 14 C, homocysteine, and serine dehydratase preparations. The formation of this product interferes with commonly used assays of serine dehydratase, which are based on the serine, pyruvic acid, or homocysteine content of incubation mixtures. Improved assay procedures have permitted the isolation of two protein fractions from rat liver by means of chromatography on hydroxylapatite. One fraction catalyzed the deamination of serine and threonine, but had no cystathionine synthase. The other catalyzed cystathionine synthesis, but had little or no deaminating activity.