Localization of O-acetyl-L-serine sulfhydrylase in Spinacia oleracea L.

Roots and hypocotyls of 11 day-old spinach seedlings with fully developed cotyledons contained 30–35% of the total O-acetyl-L-serine sulfhydrylase (OASSase) extractable from the plants.
After centrifugation of homogenates from roots on sucrose density gradients, OASSase activity was present in the fractions containing the proplastids.
In leaf extract two forms of OASSase could be detected by polyacrylamide disc gel electrophoresis. The form with the lower electrophoretic mobility in 0.1 M Tris-glycine at pH 8.4 could be attributed to the chloroplasts. The chloroplast enzyme was less stable than the extrachloroplastic form if stored without dithioerythritol (DTE).