Comparisons of cytochemical and biochemical characteristics of phagosomes and symbiotic vacuoles in xD strain of A̲m̲o̲e̲ḇa̲ p̲ṟo̲ṯe̲u̲s̲

Pure fractions of the plasmalemma, phagosomes, and symbiotic vacuoles were obtained by a newly developed procedure. The presence of functional markers was studied by enzyme cytochemistry and assay of marker enzymes in the subcellular fractions. None of the marker enzymes of the plasma membranes, i.e., (Na⁺-K⁺)-ATPase, 5'-NTPase, or alkaline phosphodiesterase, was detected, however.

Modification of the plasmalemma following phagocytosis was examined by electron microscopy. The glycocalyx was completely lost within 2 hours of endocytosis. The loss of glycocalyx and the modification of macromolecular composition were also shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Changes in the banding patterns of proteins and glycoproteins were observable more distinctly after iodination from the cytoplasmic surface of purified phagosomes by lactoperoxidase. The cytoplasmic surface of the purified symbiotic vacuoles and the phagosomes was iodinated with I-125 by lactoperoxidase. The presence of a unique protein in the membranes of symbiotic vacuoles was detected by gel radioautography. The possible role of the unique protein is discussed with respect to the maintenance of endocellular symbiosis and the inhibition of lysosomal fusion.