Chitinase Inhibitor Allosamidin Research Articles

Human serum contains a chitinase: identification of an enzyme, formerly described as 4-methylumbelliferyl-tetra-N-acetylchitotetraoside hydrolase (MU-TACT hydrolase).

Since 1988 an endoglucosaminidase, provisionally named MU-TACT hydrolase, has been known that hydrolyses the artificial substrate 4-methylumbelliferyl-tetra-N-acetyl-chitotetraoside (MU-[GlcNAc]4, where GlcNAc is N-acetylglucosamine). The biological function of the enzyme was unknown. In this paper evidence is presented showing that this endoglucosaminidase from human serum is in fact a chitinase that is different from lysozyme. The facts sustaining this finding are: (i) the identification of the products formed from MU-[GlcNAc]3 and [GlcNAc]2;and [GlcNAc]3; (ii) chitin and ethylene glycolchitin can be degraded by the enzyme; (iii) the chitinase inhibitor allosamidin also inhibits the action of MU-TACT hydrolase from human serum; (iv) no hydrolysis of the lysozyme substrate Micrococcus lysodeikticus. The enzyme also occurs in rat liver. It was demonstrated that upon Percoll density gradient centrifugation the enzyme from this tissue distributed parallel to the lysosomal marker enzymes beta-N-acetylhexosaminidase and beta-galactosidase, indicating a lysosomal localization for this enzyme. It is proposed that the enzyme functions in the hydrolysis of chitin, to which mammals are frequently exposed during infection by pathogens.

The synthesis of pseudo-sugars related to allosamizoline

The syntheses of two bicyclic pseudo-sugars related to allosamizoline, the aminocyclitol component of the chitinase inhibitor allosamidin, are described. These carbocyclic pseudo-sugars containing a cyclohexane ring were synthesised from D-glucosamine via a Ferrier rearrangement.

An enantiospecific synthesis of allosamizoline

An enantiospecific synthesis of allosamizoline 4, the aglycone of the chitinase inhibitor allosamidin 3, has been achieved, starting from readily available glucosamine. The key step in the synthesis involves the cyclisation of a carbon-centred radical onto a suitably positioned oxime ether group, thus effectively converting a carbohydrate derivative into a highly functionalised cyclopentane.

Enantiospecific total synthesis of (−)-allosamizoline, and aminocyclitol moiety of the insect chitinase inhibitor allosamidin

Total synthesis of (−)-allosamizoline ( 2), an aminocyclitol moiety of the insect chitinase inhibitor allosamidin ( 1) has been enantiospecifically synthesized from D-glucosamine by using an intramolecular cycloaddition of the nitrile oxide to an olefin as a key step.

Properties of chitin synthase in homogenates fromChironomus cells

Homogenates of Chironomus cells synthesize chitin as effectively as intact cells. Chitin is produced in a dose-dependent manner, when GlcN, GlcNAc, or UDP-GlcNAc is used as precursor. Due to the lability of UDP-GlcNAc incorporation of this substrate is underestimated. No allosteric effect is observed when GlcN 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 pH 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 trypsin treatment. Addition of protease inhibitors prevents chitin synthesis.