Pathway of chitin synthesis and cellular localization of chitin synthetase in Mocor rouxii.

Cell-free extracts of ikfucor rouxii contain enzymes which synthesize uridine diphosphate &lcetyl-D-glucosamine from IV-acetyl-n-glucosamine. Procedures are described to prepare radiolabeled UDP-GlcNAc using cell-free extracts or living cells of this fungus. This sugar nucleotide serves as the precursor for chitin synthesis. Free N-acetyl-n-glucosamine is a strong activator of chitin synthesis. Chitin synthetase activity is found in the different particulate fractions of the cell. The cell walls are particularly rich in chitin synthetase activity. Autoradiographic studies showed that chitin synthetase is localized preferentially in the apical region of hyphal walls. This is also the region of chitin deposition in vivo. The total chitin synthetase content of a culture was shown to increase concomitantly with cell growth and with the total hexosamine content of the cells.