title: Intracellular localization of serine acetyltransferase in spinach leaves.
abstract: Intact chloroplasts isolated from spinach leaves by a combination of differential and Percoll density gradient centrifugation and free of mitochondrial and peroxisomal contamination contained about 35% of the total leaf serine acetyltransferase (EC 2.3.1.30) activity. No appreciable activity of the enzyme could be detected in the gradient fractions containing broken chloroplasts, mitochondria, and peroxisomes. L-cysteine added to the incubation mixture at 1 mM almost completely inhibited serine acetyltransferase activity, both of leaf and chloroplast extracts. D-cysteine was much less inhibitory. L-cystine up to 5 mM and O-acetyl-L-serine up to 10 mM had no effect on the enzyme activity. When measured at pH 8.4, the enzyme extracted from the leaves had a K m for L-serine of 2.4, the enzyme from the chloroplasts a K m of 2.8 mM.
authors.affiliation: Pflanzenphysiologisches Institut der Universität, Altenbergrain 21, CH-3013, Bern, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Brunold
authors.forename: M
authors.initials: M
authors.lastname: Suter