STUDIES ON ROLE OF MANGANESE IN BONE FORMATION .2. EFFECT UPON CHONDROITIN SULFATE SYNTHESIS IN CHICK EPIPHYSEAL CARTILAGE

Several of the enzyme systems involved in chondroitin sulfate synthesis were examined in an attempt to explain the effect of manganese deficiency upon this polysaccharide in connective tissue. Two enzyme systems, found in 105,000g particulate fraction of epiphyseal cartilage homogenates, appear to be the critical sites of manganese function. These are as follows: (1) polymerase enzyme, which is responsible for the polymerization of UDP-N-acetyl-galactosamine and UDP-glucuronic acid to form the polysaccharide, and (2) galactotransferase, an enzyme which incorporates galactose from UDP-galactose into the galactose-galactose-xylose trisaccharide which serves as the linkage between the polysaccharide and the protein associated with it. Evidence for this conclusion is based upon the following observations: (1) Mn2+ is required for the in vitro activity of these enzyme systems. (2) Preparations from Mn-deficient chicks incorporate considerably more substrate than do comparable preparations from normal chicks. The latter is interpreted as an indication of increased available acceptor sites in the deficient tissue reflecting suboptimal in vivo enzyme activity. This conclusion is supported by differences in the composition of particulate fractions from deficient and normal tissue. These results provide a biochemical explanation for the observed effects of manganese deficiency upon the composition and histopathology of connective tissue. © 1969.