Purification, characterization and N-terminal sequence of phosphoserine aminotransferase from the green alga Scenedesmus obliquus, mutant C-2 A'.

Phosphoserine aminotransferase (EC 2.6.1.52), an enzyme of the "phosphorylated pathway" leading to the formation of serine, was purified from Scenedesmus obliquus, mutant C-2 A'. Purification started from the soluble supernatant of a crude cell homogenate and included different affinity and DEAE chromatographic techniques, as well as gel filtration. The purified phosphoserine aminotransferase was enriched 1537-fold and identified to be a homodimer with subunit molecular masses of 40 kDa, each. The absorption spectrum is consistent with the presence of pyridoxal-5-phosphate as cofactor. From the purified enzyme 18 amino acids of the N-terminus could be determined, showing at least 67% homology with the serC gene encoding phosphoserine aminotransferases from bacterial organisms.