J. Biol. Chem., Vol. 261, Issue 7, 3229-3232, Mar, 1986
The phospholipase A1 of Trypanosoma brucei does not release myristate from the variant surface glycoprotein
PN Hambrey, CM Forsberg and A Mellors
[3H]Myristoyl-labeled variant surface glycoprotein (VSG) has been isolated
from Trypanosoma brucei by reverse phase high performance liquid
chromatography and used as substrate for the conversion by trypanosomal
enzymes of membrane-form VSG to soluble VSG. Conversion is detected by the
release of myristoyl-containing lipids. The major lipolytic enzyme of T.
brucei, phospholipase A1, is effective for the hydrolysis of myristoyl
esters of p-nitrophenol, in a colorimetric assay. However, the
phospholipase is unable to cleave the myristoyl ester linkage of VSG. The
phospholipase can be separated from the myristoyl-releasing activity of
trypanosome homogenate by centrifugation, affinity chromatography, and
anion-exchange chromatography. Elution profiles on anion-exchange high
performance liquid chromatography also indicate that the phospholipase is
inactive against VSG. A small amount of myristoyl-releasing activity
associated with the purified phospholipase is probably due to contamination
with a phosphodiesterase which releases myristoyl-containing diglyceride
from VSG.