Homogenates of Chironomus cells synthesize chitin as effectively as intact cells. Chitin is produced in a dose-dependent manner, when GlcN, ClcNAc, or UDPGlcNAc is used as precursor. Due to the lability of UDP-GlcNAc incorporation of this substrate is underestimated. N o allosteric effect i s observed when ClcN or GlcNAc is used as a substrate. Chitin synthesis is stimulated by Mg2+ and inhibited by uridine monophosphate (UMP), uridine diphosphate (UDP), and uridine triphosphate (UTP). The apparent temperature optimum is 30"C, the apparent p H optimum is 5.5-6. Addition of the chitinase inhibitor allosamidin does not enhance chitin synthesis significantly. The time course of chitin formation reveals a lag period of about 12 h, which can be overcome by t rypsi n treatment . Addition of protease i n h i bitors prevents chitin synthesis .

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