Enzymes regulating glucosamine 6-phosphate synthesis in the zygote of Ascaris suum

Dubinský P., Rybo? M. and Tur?eková ?. 1985. Enzymes regulating glucosamine 6-phosphate synthesis in the zygote of Ascaris suum. International Journal for Parasitology15: 415–419. Formation of glucosamine 6-phosphate, a basic intermediate product of chitin synthesis in the zygote of Ascaris suum is catalyzed by glutamine-fructose-6-phosphate aminotransferase (EC 2.6.1.16). The highest activity of the enzyme was observed immediately after fertilization of mature oocytes. High enzyme activity also found in unfertilized oocytes indicates that formation of glucosamine 6-phosphate is catalyzed by enzymes that were present in the oocytes prior to their fertilization. In the Ascaris suum zygote, in contrast to the situation in other organisms, glucosaminephosphate isomerase (EC 5.3.1.10) plays no part in glucosamine 6-phosphate synthesis. The paper discusses possible participation of glucosaminephosphate isomerase in the resynthesis of fructose 6-phosphate from the surplus glucosamine 6-phosphate not utilized for chitin synthesis, and accordingly its involvement in the metabolism of the zygote.