Chitin synthetase

Nikkomycins. The nikkomycins (141—159), isolated from S. tendae are nucleoside-peptide antibiotics (1,4,244,245) as shown in Table 8. Nikkomycins X and Z are stmcturaHy identical to neopolyoxins A and C, respectively. Compound (141) is a competitive inhibitor of chitin synthetase. Two new nikkomycins, nikkomycin pseudo-Z and pseudo-J (158, 159), contain a C-glycosidic bond between C-5 of uracil and C-1 of... 

Chitin synthetase -inhibition of [ANTIBIOTICS - NUCLEOSIDES AND NUCLEOTIDES] (Vol 3)... 

After injection, when part of the permeability barriers in the larvae is absent, polyoxin D inhibits the glucose incorporation, but less so than difluben-zuron. The conclusion seems obvious that the intrinsic effects of both compounds are practically identical but that polyoxin D is much more hindered by the permeability barriers present in the Pieris brassicae larvae. On the strength of the evidence presented by Misato and co-workers that polyoxin D is a competitive inhibitor of chitin synthetase, a... 

Summarizing, diflubenzuron features mentioned in the introduction of this paper can be completed as follows The new insecticide has favourable environmental properties because it is non-persistent in soils and it has a low biological magnification. It is stable on plants and in insects, hence it has a long residual activity. It represents the best choice from the series of the benzoylphenyl ureas. It is a reversible inhibitor of chitin synthesis in insects, probably by blocking chitin synthetase. 

Polyoxlns. The polyoxin antibiotics are effective against fungi that contain chitin in their cell walls. The resistance to polyoxlns in some fungi of this type appears to be related to a permeability factor rather than to a change in the site of action (14). Polyoxlns competitively inhibit chitin synthetase and thus prevent the incorporation of uridinediphospho-N-acetylglucosamine into the chitin polymer (14). 

Polyoxins are peptide-nucleosides that are substrate analogs of UDP-N-acetylglucosamine wliich is the essential building block of chitin, this polymer making up 1% of the yeast cell wall. Polyoxins have been used in agriculture for many years and act by inhibiting chitin synthetase. 

Lufenuron is a benzoylurea compound with chitin synthetase inhibitory activity that is used principally as a systemic insecticide. Given orally to horses, at a dose rate of 5 mg/kg once daily, lufenuron may be beneficial when used in combination with topical antifungal agents. The potential toxicity of this compound in the horse has not been investigated. 

As mentioned, the insecticides inhibit chitin synthesis indirectly and they are not useful as fungicides. Polyoxins, however, are structural analogues to uridine diphospate-2-acetamido-2-deoxy-D-glucose, which is the substrate for chitin synthetase, and inhibit the incorporation of 2-aceta-mido-2-deoxy-D-glucose into chitin. It is produced by fermentation of Strep-tori n/ces cacaoi var. asoensis. It is used as a fungicide against powdery mildews in apples and pears, and for many other purposes. Its mammalian toxicity is very low, and it has a no-observed-effect level (NOEL) in rats of 44,000 mg/kg in diet in 2-year studies. The compounds inhibit chitin synthetase from insects, but are not toxic to insects in vivo. 

---