PURIFICATION AND PARTIAL CHARACTERIZATION OF ACYL CARRIER PROTEINS FROM DEVELOPING OIL SEEDS OF PISA (ACTINODAPHNE HOOKERI) AND GROUND NUT (ARACHIS-HYPOGAEA)

Acyl carrier proteins (ACP) were purified to homogeneity in the active form from developing seeds of pisa (Actinodaphne hookeri) which synth esizes exclusively trilaurin and from ground nut (Arachis hypogaea) wh ich synthesizes triacylglycerols containing long chain fatty acids. Tw o major isoforms of ACPs were purified from developing pisa seeds usin g DEAE-cellulose, Superose-6 FPLC and C-4 reversed phase HPLC chromato graphic methods. In contrast, only a single form of ACP was present in ground nut seeds which was purified by anion-exchange and activated t hiol-Sepharose 4B affinity chromatography. The two isoforms of ACPs fr om pisa showed nearly the same specific activity of 6,706 and 7,175 pm ol per min per mg protein while ground nut ACP showed a specific activ ity of 3,893 pmol per min per mg protein when assayed using E. coli ac yl-ACP synthetase and [1-C-14]palmitic acid. When compared with E. col i ACP, the purified ACPs from both the seeds showed considerable diffe rence in their mobility in native PAGE, but showed similar mobility in SDS-PAGE under reducing conditions. In the absence of reducing agents formation of dimers was quite prominent. The ACPs from both the seed sources were acid- and heat-stable. The major isoform of pisa seed ACP and the ground nut ACP contain 91 amino acids with M(r) 11,616 and 1, 228 respectively. However, there is significant variation in their ami no acid composition. A comparision of the amino acid sequence in the N -terminal region of pisa and ground nut seed ACPs showed considerable homology between themselves and with other plant ACPs but not with E. coli ACP.