Depolymerase Depolymerisation

On the other hand, the biological method of depolymerisation uses either the intracellular [246] or extracellular depolymerases [214]. It has also been shown that the intracellular PHA depolymerisation mechanisms can be exploited in vivo to generate (R)- monomers from PHAscl and PHAmcl accumulated by several bacteria such as A. latus, R. eutropha, P. oleovorans and P. aeruginosa [247]. 

Several kinds of extracellular depolymerases have been purified and characterised from various microorganisms [187, 189,191, 195-197], All the depolymerases are comprised of an N-terminal catalytic domain, a C-terminal substrate binding domain, and a linker region connecting the two domains. Similar catalytic and binding domains have also been identified in other depolymerising enzymes that hydrolyse water-insoluble polysaccharides such as cellulose [198], xylan [198,199], and chitin [200], The catalytic domain contains a lipase box pentapeptide [Gly-Xi-Ser-X2-Gly] as the active site, which is common for serine hydrolase [201]. Further detailed aspects on the structure and mechanisms of PHA depolymerase (EC 3.1.1.76) can be found elsewhere [202]. 

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