Pyrococcus furiosus (thermophilic archaea)
The optimum growth temperature of the hyperthermophilic archaeon Pyrococcus furiosus (Pfu) is around 100 degree Celsius. Proteins from this species naturally work at such a high temperature. Chitinase [EC 220.127.116.11] is an enzyme that can hydrolyze the beta-1,4 linkage between N-acetyl-D-glucosamine (NAG) in chitin and expected to be useful for the utilization of chitin on an industry. Chitin, an insoluble, linear beta-1,4-linked polymer of NAG, is a common constituent of fungal cell-walls, the exoskeletons of insects and the shells of crustaceans, being the second most abundant polysaccharide in biomass. NAG and its oligosasshrides derived from chitin are expected to be useful as food additives and medicines. Originally, the chitinase gene of Pyrococcus furiosus existed as a pseudo-gene on the genome due to a frame shift mutation on its gene. By artificially removing the frame shift, the hydrolyzing activity as the chitinase was successfully recovered.
This artificial chitinase (Pf-Chitinase) is a thermostable enzyme, being composed of two catalytic domains and two chitin-binding domains (ChBDs) (one of the ChBDs is registered in PDB as 2cwr (crystal structure) and 2czn (solution structure)). In these domains, the catalytic domain (AD2) showed a strong hydrolyzing activity toward crystal chitin.
The overall structure of this domain is a TIM-barrel (beta/alpha) 8-fold with a groove-like active site architecture, which is a typical feature of endo-chitinases. This architecture is similar to the plant-type chitinases.
Protein Data Bank (PDB)
author: Koichi Uegaki