Disease relevance of AO3

• Plasmodium chitinase activities are demonstrated targets for human and avian malaria transmission blockade with the chitinase inhibitor allosamidin [1].
• Chitinases insensitive to allosamidin were detected in the culture supernatants of all tested Streptomyces species [2].
• Structure of the D142N mutant of the family 18 chitinase ChiB from Serratia marcescens and its complex with allosamidin [3].

High impact information on AO3

• Thus far, only one potent chitinase inhibitor has been described in detail, the pseudotrisaccharide allosamidin [4].
• Chitinases (EC 3.2.1.14) are critical for parasite invasion of the midgut: the presence of the chitinase inhibitor, allosamidin, in an infectious blood meal prevents oocyst development [5].
• Homology modeling predicts that PgCHT1 has a novel pocket in the catalytic active site that PfCHT1 lacks, which may explain the differential sensitivity of PfCHT1 and PgCHT1 to allosamidin [5].
• Allosamidin ablates activity of the native enzyme in a dose-dependent manner but did not significantly inhibit the moulting of L3 larvae [6].
• Since the peritrophic matrix is a physical barrier that the parasite must cross to invade the mosquito, and the presence of allosamidin, a chitinase inhibitor, in a blood meal prevents the parasite from invading the midgut epithelium, chitinases (3.2.1.14) are potential targets of malaria parasite transmission-blocking interventions [7].

Biological context of AO3

• The pseudotrisaccharide allosamidin is a potent family 18 chitinase inhibitor with demonstrated biological activity against insects, fungi, and the Plasmodium falciparum life cycle [8].
• Stereochemistry of chitin hydrolysis by a plant chitinase/lysozyme and X-ray structure of a complex with allosamidin: evidence for substrate assisted catalysis [9].
• Allosamidin, a specific chitinase inhibitor, inhibited activity from both strains, with IC50 values of about 50 microM with colloidal chitin as substrate and between 1 and 10 microM with 4-methylumbelliferyl-diacetylchitobioside and 4-methylumbelliferyl-triacetylchitotrioside as substrates [10].
• Presence of 100 microM allosamidin increased the LD50 by factors of 1.3 and 1.4, respectively, demonstrating a role for bacterial chitinases in the attack on the insects [10].
• Allosamidin strongly inhibited the three enzyme forms with different kinetics [11].

Anatomical context of AO3

• A transformation system for Streptomyces sp. AJ9463 strain (allosamidin producer) was successfully developed using protoplasts and a PEG-mediated method [12].

Associations of AO3 with other chemical compounds

• The enzyme was not inhibited by allosamidin, the natural inhibitor of chitinolytic activity, and was also resistant to denaturation by urea and SDS [13].
• Four chitinase inhibitors, cyclo-(Proline-Tyrosine), cyclo-(Histidine-Proline), allosamidin and psammaplin A, were selected for in vitro feeding experiments with the peach-potato aphid, Myzus persicae (Sulzer), under controlled photoperiod and temperature conditions [14].

Gene context of AO3

• The chitinase requirement for lysis has been confirmed in two different ways: (a) demethylallosamidin, a more powerful chitinase inhibitor than the previously used allosamidin, is also a much better protector against lysis and (b) disruption of the chitinase gene in chs1 cells eliminates lysis [15].
• The chitotriosidase was shown to be active against colloidal chitin and is inhibited by the family 18 chitinase inhibitor allosamidin [16].
• Recombinant expression of the cloned cDNA demonstrated that the encoded protein is secreted and has chitinolytic activity that is sensitive to the specific chitinase inhibitor allosamidin and has the ability to bind to chitin particles [17].
• 5. At higher, micromolar, concentrations, allosamidin inactivated this chitinase in a time- and concentration-dependent manner [18].

Analytical, diagnostic and therapeutic context of AO3

• The structural interactions of allosamidin with several family 18 chitinases have been determined by x-ray crystallography previously [8].
• De novo purification scheme and crystallization conditions yield high-resolution structures of chitinase A and its complex with the inhibitor allosamidin [19].

References