Sj. Cai et al., RAPID PURIFICATION OF COTTON SEED MEMBRANE-BOUND N-ACYLPHOSPHATIDYLETHANOLAMINE SYNTHASE BY IMMOBILIZED ARTIFICIAL MEMBRANE CHROMATOGRAPHY, Journal of chromatography, 696(1), 1995, pp. 49-62
N-Acylphosphatidylethanolamine synthase (NAPES) is a membrane-bound en
zyme present in cotton seedlings at a concentration of less than or eq
ual to 0.02% of the total protein. NAPES was purified to electrophoret
ic homogeneity in a single chromatographic step using immobilized arti
ficial membrane (IAM) chromatography. The IAM column used for NAPES pu
rification was (ether)IAM.PE(C10/C3) and this surface contains a monol
ayer of immobilized phosphatidylethanolamine (PE). Since PE is an anal
ogue of the natural substrate for NAPES, (ether)IAM.PE(C10/C3) columns
function as an affinity column for this enzyme. Detergent-solubilized
microsomal proteins from cotton were loaded on to the (ether)IAM.PE(C
10/C3) column and eluted with buffered mobile phases containing 0.2 mM
dimyristoylphosphatidylethanolamine (DMPE) and 2 mM dodecylmaltoside.
Little NAPES functional activity eluted if DMPE was removed from the
mobile phase. Mobile phase DMPE is also a substrate for NAPES, and the
refore both the mobile phase and IAM surface contains NAPES substrates
. Mobile phase DMPE may function as both a surfactant-type affinity di
splacing ligand effecting protein elution and also a stabilizing facto
r of NAPES functional activity. The loading capacity on semi-preparati
ve (ether)IAM.PE(C10/C3) (6.5 X 1.0 Cm) columns was ca. 5 mg of total
detergent solubilized microsomal proteins, and protein recovery was qu
antitative. This one-step IAM purification of NAPES resulted in a sing
le band on silver-stained polyacrylamide gels, and 3940 fold increase
in NAPES specific activity. The molecular mass of the purified NAPES p
rotein is 64000. I-125 labeled [12-(4-azidosalicyl)amino]dodecanoic ac
id is a photoreactive fatty acid substrate of NAPES that was used to c
onfirm protein purity.