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 ''phosp horylated pathway'' leading to the formation of serine, was purified f rom 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 filtrati on. 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 a cids of the N-terminus could be determined, showing at least 67% homol ogy with the serC gene encoding phosphoserine aminotransferases from b acterial organisms.