ISOLATION OF beta-GLUCAN SYNTHETASE PARTICLES FROM PLANT CELLS AND IDENTIFICATION WITH GOLGI MEMBRANES.

A variety of particle-bound synthetases that use sugar nucleotides as glycosyl donors for the formation of polysaccharides similar to those of the cell wall have been demonstrated in mung beans and other plant tissues,(1) but the particles in question have not been previously identified.(2, 3) The polysaccharide synthetase particles from peas that form mainly beta-1,4-glucan from UDPG and GDPG have now been separated from other cell particles by combinations of velocity and isopycnic density gradient centrifugation. The particles have an effective density of about 1.15 gm cm(-3), exhibit latent nucleoside diphosphatase activity upon IDP, UDP, GDP, and to a lesser extent upon ADP, and also possess acid phosphatase and weak ATPase activity. The isolated synthetase particles consist of somewhat condensed Golgi dictyosomes and free dictyosomal membranes bearing vesicles. It is concluded that the synthetase particles are Golgi membranes. The nucleoside diphosphatase activity of these particles may represent inactivated polysaccharide synthetase.