Biosynthesis of the Polysaccharide of Micrococcus Cell Walls lysodeikticus I. CHARACTERIZATION OF AN IN VITRO SYSTEM FOR POLYSACCHARIDE BIOSYNTHESIS*

The particulate enzyme fraction obtained from Micrococcus Zysodeikficus catalyzed the incorporation of D-[r4C]glucose from uridine diphospho-n-[r4C]glucose into a polymer which resembled the n-glucoseand N-acetyl-n-mannosaminuronic acid-containing polysaccharide of the cell walls of this organism. In vifro biosynthesis of the polysaccharide depended upon the presence of the uridine diphospho-Nacetylhexosaminuronic acid fraction isolated from 2M. lysodeikficus and uridine diphospho-N-acetyl-n-glucosamine and was stimulated by a heat-stable factor obtained from the soluble fraction of cell extracts. The reaction proceeded optimally at pH 8.2 and at 20 mr+r magnesium ion concentration. The incorporation of n-[14C]glucose proceeded after a lag period of 15 to 20 min. Preincubation of the reaction components with the particulate enzyme fraction before the addition of uridine diphospho-n-glucose eliminated the lag period. [14C]N-Acetylhexosaminuronic acid residues were incorporated into polysaccharide from [r4C]uridine diphospho-Nacetylhexosaminuronic acid (labeled throughout the molecule) in an amount approximately equimolar to D-glucose in a reaction dependent upon uridine diphospho-D-glucose. However, when uridine diphospho-N-[14C]acetyl-rr-glucosamine was the labeled substrate, N-[14C]acetyl-D-glucosamine was incorporated only to the extent of 1 residue or less for each 15 residues of n-glucose.